Heat Shrink Tubing Glossary
Choosing heat shrink comes down to a handful of specs: shrink ratio, recovered size, wall type, material and ratings. This glossary explains each term in plain English and links to the products that match, so you can go from a datasheet spec to the right part. New to heat shrink? Start with our overview of the types of heat shrink and what they're for.
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Sizing & Fit
These terms explain how heat shrink sizes are listed and how to choose a size that fits.
Shrink Ratio
The relationship between the tubing's size as supplied and its size after full recovery, written as original size : recovered size. 2:1 tubing shrinks to half its supplied diameter, 3:1 to one third, 4:1 to one quarter and 6:1 to one sixth. Higher ratios cover a larger difference between the biggest and smallest points of a part, such as a connector on a thin wire, with a single size. Shop 2:1 heat shrink, 3:1 polyolefin heat shrink, 4:1 polyolefin heat shrink or 6:1 high-ratio heat shrink.
Expanded Inside Diameter (Supplied ID)
The inside diameter of the tubing as you receive it, before heating. This is the size in the product name (for example, 1/4" heat shrink). It must be larger than the largest point the tubing has to slide over.
Recovered Inside Diameter
The largest inside diameter the tubing will have after it is fully shrunk with nothing inside it. To grip tightly, the recovered ID must be smaller than the smallest point you are covering.
Use Range (Fit Range)
The span between the recovered ID and the expanded ID: every diameter a given size can cover. As a rule of thumb, choose an expanded ID at least 10–20% larger than the largest point and a recovered ID at least 10–20% smaller than the smallest point. Avoid sizing right at either limit; tubing that has room left to shrink grips tighter and seals better. Not sure of your dimensions? See how to measure cable diameter.
Sizing example: You need to cover a connector that is 0.40" at its widest on a wire that is 0.20" across. 1/2" 3:1 tubing has a 0.50" expanded ID (25% larger than the connector) and recovers to about 0.17" (smaller than the wire), so it covers both. 1/2" 2:1 tubing would only recover to 0.25" and would stay loose on the wire.
Recovered Wall Thickness
The wall thickness after shrinking. Walls get thicker as tubing recovers, so manufacturers list wall thickness in the recovered state. Recovered wall thickness drives insulation, abrasion resistance and flexibility.
Longitudinal Change
How much the tubing shortens lengthwise as it shrinks, usually a few percent and higher on some high-ratio and adhesive-lined tubing. Check the datasheet and cut each piece a little longer than the area you need to cover.
AWG (American Wire Gauge)
The U.S. standard for wire conductor size. A smaller AWG number means a thicker wire. Because insulation thickness varies, size heat shrink by measuring the wire's outside diameter rather than going by gauge alone. Here's how to measure cable diameter. Our heat shrink butt connectors are color-coded by AWG range.
Spools, Pre-Cut Pieces & Bulk
Heat shrink comes on continuous spools and rolls for production work, in pre-cut pieces for quick jobs, in assorted kits, and in bulk quantities for high-volume buyers.
Construction & Wall Types
Tubing construction determines whether it seals, how stiff it is, and how much protection it gives.
Single Wall Heat Shrink
Tubing with no inner adhesive. It is used for insulation, strain relief, bundling, color coding and general protection where a waterproof seal isn't required. See all single wall heat shrink tubing, or read why it outperforms tape in heat shrink tubing vs. electrical tape.
Dual Wall / Adhesive-Lined Heat Shrink
These terms mean the same thing: tubing with an outer jacket and an inner layer of hot-melt adhesive. When heated, the jacket shrinks while the adhesive melts and flows into gaps, bonding to the substrate. The result is an environmental seal against moisture, dust and corrosion. Because the adhesive takes up space, adhesive-lined tubing usually comes in ratios of 3:1 or higher. It is the standard choice for marine, automotive and outdoor connections. Shop dual wall adhesive-lined heat shrink, 3:1 thin wall adhesive-lined or 4:1 adhesive-lined heat shrink, or browse products for boats and marine craft. For a real-world example, see how to waterproof swimming pool wiring.
Hot-Melt Adhesive
The thermoplastic adhesive inside dual wall tubing, end caps and splices. It softens and flows during recovery, then sets as it cools. It is also available separately as hot melt glue and hot melt tape for heat shrink tubing.
Thin Wall & Ultra-Thin Wall
Low-profile tubing that stays flexible and adds very little bulk. It is ideal for wire harnesses, tight spaces and components where size matters. See ultra-thin wall polyolefin and 2:1 thin wall heat shrink.
Medium Wall
A balance of flexibility and mechanical protection, often adhesive-lined. It is common on cable splices and connectors. See 3:1 medium wall adhesive-lined heat shrink.
Heavy Wall
Thick-walled tubing for maximum abrasion, impact and environmental protection, for example on battery cables, power cable splices and industrial equipment. See 3:1 heavy wall adhesive-lined heat shrink and Canusa CFW-U heavy wall (unlined).
Flexible vs. Semi-Rigid
Flexible tubing bends with the wire. Semi-rigid tubing holds its shape after recovery, which makes it useful for strain relief, protecting solder joints and keeping components aligned. See 3:1 semi-rigid adhesive-lined heat shrink.
Dual Shrink (FEP/PTFE)
Not the same as dual wall. Dual shrink tubing has a PTFE outer layer and an FEP inner liner. During recovery the outer layer shrinks while the inner liner melts, encapsulating the part in a moisture-tight, high-temperature covering. See FEP/PTFE dual shrink tubing.
Pre-Flattened / Printable Heat Shrink
Tubing supplied flat so it can feed through a thermal transfer printer and come out as a permanent wire or cable ID marker. See pre-flattened heat shrink, 3:1 printable heat shrink and our custom heat shrink printing service.
Slit / Wrap-Around Tubing
Tubing or sleeving with a lengthwise opening, so it can be installed over wiring that's already terminated without removing connectors. Learn more about shrink wrap and slit tubing.
Materials
Heat shrink materials at a glance (typical values, check the product datasheet)
| Material | Typical shrink ratios | Continuous operating temp. | Best for |
|---|---|---|---|
| Polyolefin | 2:1 to 6:1 | −55 to 125 °C | General purpose, color coding, sealing (adhesive-lined) |
| PVC | 2:1 | Up to ~105 °C | Economical insulation and bundling |
| PVDF (Kynar®) | 2:1 | Up to ~175 °C | Semi-rigid strain relief, solder joints |
| Viton® | 2:1 | Up to ~200 °C | Fuel, oil and hydraulic fluid exposure |
| FEP | 1.3:1 to 1.6:1 | Up to ~200 °C | Clear, chemically inert covers |
| PTFE (Teflon™) | 2:1 to 4:1 | Up to ~260 °C | Highest temperatures, low friction |
Material sets the temperature range, chemical resistance, flexibility and cost of heat shrink. Temperatures below are typical; always confirm on the product datasheet.
Polyolefin
The most widely used heat shrink material. It is flexible, economical and available in many colors, ratios and wall thicknesses, usually in flame-retardant grades. General-purpose polyolefin typically starts shrinking around 70 °C (158 °F), fully recovers around 110–125 °C, and is commonly rated for continuous use from −55 °C to 125 °C. Shop 2:1 polyolefin, 3:1 polyolefin and 4:1 polyolefin heat shrink.
Cross-Linking & Elastic Memory
Heat shrink is made by cross-linking a plastic (often by irradiation), then expanding it while hot and cooling it in the expanded state. Heating it again releases this "elastic memory," and the tube returns to its original extruded size, which is the recovered ID.
PVC (Polyvinyl Chloride)
An economical, glossy, flexible heat shrink, usually 2:1. It has a lower temperature rating than polyolefin (commonly up to about 105 °C). PVC contains chlorine, so it isn't suitable where halogen-free materials are required. See PVC heat shrink tubing and ultra-thin wall PVC.
PTFE (Teflon™)
The highest-temperature heat shrink material, with continuous ratings around 260 °C. It is chemically inert and has a very low friction surface. PTFE needs much higher temperatures to recover (around 340 °C and up), so plan on a high-temperature heat gun or oven. See PTFE heat shrink tubing and adhesive-lined PTFE.
FEP (Fluorinated Ethylene Propylene)
A clear fluoropolymer with excellent chemical resistance and a continuous rating of about 200 °C. It recovers at lower temperatures than PTFE. FEP comes in low shrink ratios such as 1.3:1 and 1.6:1 and is often used for roller covers and medical or lab components. See all FEP heat shrink tubing.
PVDF (Kynar®)
A tough, clear, semi-rigid fluoropolymer rated to about 175 °C. It offers strong abrasion, cut-through and chemical resistance and is used for strain relief and protecting solder joints. See semi-rigid Kynar heat shrink.
Viton® (Fluoroelastomer)
A flexible, rubber-like heat shrink with outstanding resistance to fuels, oils, hydraulic fluids and solvents at high temperature. It is common in aerospace, military and motorsport harnesses. See Viton heat shrink tubing.
Neoprene (Polychloroprene)
A flexible, tough elastomeric tubing with good abrasion and oil resistance, used for rugged cable jacketing and harness protection. See neoprene shrink tubing.
Diesel-Resistant Elastomer
Elastomeric tubing formulated to withstand diesel fuel, lubricants and hydraulic fluids in engine bays and heavy equipment. See diesel-resistant heat shrink.
Fluoropolymer
The material family that includes PTFE, FEP, PVDF and ECTFE (Halar®). Fluoropolymers share high temperature ratings and broad chemical resistance. Browse high-temperature heat shrink or 2:1 flexible fluoropolymer tubing.
Fabric & Grip Heat Shrink
Specialty tubing for handles and high-wear areas. Fabric heat shrink adds a woven, abrasion-resistant covering, and textured grip heat shrink adds a non-slip surface to tools, handles and equipment.
Temperature Terms
Three different temperatures appear on heat shrink datasheets, and they are easy to confuse.
Shrink (Activation) Temperature
The temperature at which the tubing begins to shrink. Reaching it doesn't mean the tubing has fully recovered.
Full Recovery Temperature
The temperature needed for the tubing to shrink all the way to its recovered ID and, for adhesive-lined tubing, for the adhesive to flow. Make sure your heat source can reach it.
Operating Temperature Range
The continuous temperature range the installed tubing can withstand over its service life, for example −55 °C to 125 °C for general-purpose polyolefin.
Low Shrink Temperature
Tubing that fully recovers at a much lower temperature, around 80 °C (176 °F). Use it over heat-sensitive components, plastics and assemblies that standard tubing could damage. See low shrink temperature (80 °C) heat shrink.
Electrical & Performance Properties
These properties describe how heat shrink performs once it's installed.
Voltage Rating
The maximum continuous voltage the tubing is rated to insulate. Many general-purpose polyolefin tubes are rated 600 V. Medium- and high-voltage applications need products designed and rated for them.
Dielectric Strength
The voltage an insulating material can withstand per unit of thickness before it breaks down electrically, usually given in volts per mil (V/mil) or kV/mm. It is measured on the recovered wall, so thicker walls withstand higher voltages.
Flame Retardant
Formulated to resist ignition and self-extinguish once the flame source is removed. Look for a recognized rating such as VW-1 rather than the term alone. Flame-retardant versions are also available in braided sleeving. Learn more about electrical fire safety.
Halogen-Free / Low Smoke Zero Halogen (LSZH)
Materials made without chlorine, bromine or other halogens. When burned they produce less dense, less toxic and less corrosive smoke, which matters in mass transit, data centers, ships and other enclosed spaces. PVC and fluoropolymers are not halogen-free.
UV Resistance
The ability to withstand prolonged sunlight without cracking or becoming brittle. For outdoor installations, black polyolefin is generally the most UV-stable choice.
Chemical & Fluid Resistance
Resistance to fuels, oils, solvents and cleaning agents. Fluoropolymers and elastomers such as Viton lead this category, and general-purpose polyolefin handles most common exposures.
Abrasion Resistance
The ability to resist wear from rubbing, vibration and contact with edges. Heavy wall tubing, semi-rigid PVDF and abrasion-resistant nylon sleeving perform best.
EMI/RFI Shielding
Shielding that blocks electromagnetic and radio-frequency interference from entering or leaving a cable. See EMI/RFI shielding heat shrink and metal and conductive braid.
Limiting Oxygen Index (LOI)
The minimum oxygen concentration, as a percentage, needed to keep a material burning. Air is about 21% oxygen, so materials with an LOI below 21 burn readily in normal air, and materials above roughly 26–28 are generally considered self-extinguishing. Typical approximate values: polyethylene and polypropylene ≈17; nylon 6/6 ≈24–28; Nomex® ≈28–30; rigid PVC ≈45–49; ECTFE (Halar®) ≈60–64; PTFE ≈95.
Standards & Ratings
These are the certifications and specifications you'll see on product pages and datasheets.
UL 224
The UL standard for extruded insulating tubing, the standard most heat shrink tubing is recognized under. It covers temperature ratings, voltage ratings and physical and electrical properties, with optional flame ratings such as VW-1. You can look up any product's UL certification with the free UL Product iQ search.
VW-1 (Vertical Wire Flame Test)
A UL flame test in which a flame is applied repeatedly to a vertical sample. To pass, the sample must self-extinguish within set limits, must not burn more than 25% of a paper indicator flag, and must not drop burning particles that ignite cotton below it. "UL 224 VW-1" on a product means it passed this test.
UL 94 (V-0, V-1, V-2, HB)
Flammability ratings for plastic materials. V-0 is the most stringent of the vertical ratings: the sample stops burning within 10 seconds with no flaming drips. V-1 allows 30 seconds with no flaming drips, and V-2 allows 30 seconds with flaming drips. HB is a slower-burning horizontal rating. You'll see UL 94 ratings on parts such as nylon cable ties.
UL 1441
The UL standard for coated electrical sleeving, such as vinyl- and silicone-coated fiberglass sleeving. Like UL 224, it can include a VW-1 flame rating.
CSA C22.2 No. 198.1
The Canadian standard for extruded insulating tubing, the Canadian counterpart to UL 224. Products listed to both carry UL and CSA (or cUL) markings.
SAE-AMS-DTL-23053 (Mil-Spec Heat Shrink)
The aerospace and military specification for heat shrink tubing, formerly MIL-I-23053 / MIL-DTL-23053 (sometimes referred to as M23053). Slash sheets define each material: for example /5 is flexible polyolefin, /8 is PVDF (Kynar), /11 is FEP, /12 is PTFE, /13 is elastomer (Viton) and /1 is neoprene. See Dunbar mil-spec heat shrink and products for aerospace and military applications, and read how heat shrink and mil-spec keep systems airworthy.
QPL (Qualified Products List)
The U.S. government list of products formally qualified to a military specification. "QPL-approved" means the specific product has been tested and listed, not just made to the spec. Examples include Dunbar 1635F 2:1 and Dunbar 3635W 3:1 adhesive-lined.
RoHS & REACH
European Union regulations that restrict hazardous substances in electrical and electronic products (RoHS) and in chemicals and materials generally (REACH). Compliance is often required for products sold into the EU.
Plenum & Plenum-Rated
A plenum is a space used for air handling and distribution in a building, such as the area above a drop ceiling or below a raised floor. Under the National Electrical Code (NEC Article 300.22), materials installed there must meet stricter fire and smoke requirements. For discrete products like cable ties, that typically means testing to UL 2043. See plenum-rated Halar cable ties and air-handling cable ties. Related: protecting HVAC wiring.
Heat Shrink Product Types
Heat shrink also comes pre-formed into parts made for specific jobs.
End Caps
Closed-end, adhesive-lined heat shrink caps that seal and insulate cut cable ends, unused conductors and stub splices. See heat shrink end caps or the 3:1 adhesive-lined heat shrink end cap. End caps also work beyond electrical, for example in finishing rope ends for gyms and facilities.
Solder Sleeves
Clear heat shrink sleeves with a preloaded solder ring and adhesive sealing rings. One application of heat solders, insulates and seals a wire splice or shield termination. See solder sleeves.
Heat Shrink Butt Splices
Crimp connectors covered in adhesive-lined heat shrink that join two wires end-to-end with a sealed, insulated connection. See heat shrink butt splices and high-temperature butt splices.
Heat Shrink Terminals
Crimp terminals with a sealing heat shrink sleeve, available as ring terminals, spade/fork terminals, hook terminals, quick disconnects and step-down and multi-way connectors.
Boots, Breakouts & Y-Shapes
Molded heat shrink shapes that seal connector backshells and the points where cables split into branches. Learn about Y-shaped heat shrink.
Heat Shrink Tape
A wrap-on heat shrinkable tape for irregular shapes, long runs and repairs where tubing can't be slid on. See heat shrink tape.
Heat Shrink Bands
Clear or printed tamper-evident bands that shrink around bottle and jar caps. See heat shrink bands.
Heat Shrink Wire Markers & Labels
Printable heat shrink sleeves that become permanent cable identification. See heat shrink wire markers and label and heat shrink printers.
Cold Shrink
Rubber tubing (silicone or EPDM) that is pre-stretched over a removable core. Pull out the core and the tube contracts onto the part, with no heat required. It is useful where open flame or heat guns aren't allowed. See cold shrink tubing and end caps.
Non-Shrink Tubing
Plastic tubing that does not change size when heated, used for sleeving, spacing and fluid transfer. See non-shrink plastic tubing.
Installation & Tools
These terms come up when you're shrinking tubing and choosing tools.
Recovery
The process of heating tubing until it shrinks to fit. Apply heat evenly, rotating the part. Starting in the middle and working outward, or from one end to the other, pushes out trapped air. See how this compares with taping in heat shrink tubing vs. electrical tape.
Adhesive Flow (Bead)
A small bead of adhesive visible at both ends of dual wall tubing or splices after recovery. It shows the adhesive has melted and the joint is sealed.
Heat Gun
The standard tool for shrinking tubing, which delivers controlled hot air. Choose from electric heat guns for the bench and butane heat tools for portable field work. High-temperature materials such as PTFE need guns that reach their recovery temperature.
Heat Shrink Oven
An enclosed oven that recovers many pieces evenly at once, used in production. See the heat shrink oven.
Hot Knife & Tubing Cutters
Tools that cut tubing cleanly and square. A clean cut matters, because nicks and ragged edges are the most common cause of splitting. See heat shrink cutting machines and the bench-mount hot knife cutter.
Splitting & Scorching
Common installation failures. Splitting usually starts at a nicked edge, sharp edges on the part, or tubing sized too close to its expanded ID. Scorching, discoloration and bubbling come from overheating, so move the heat source steadily and avoid open flame on thin wall tubing.
Still not sure which heat shrink you need?
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Further reading: Types of heat shrink & what they're for · How to measure cable diameter · Heat shrink tubing vs. electrical tape · All articles
Heat Shrink Terminology
