Our 3:1 heavy wall adhesive lined heat shrink tubing is ideal for direct burial of heavy duty electrical cables, where environmental protection is necessary. This high quality heat shrinkable tubing is supplied with an inner adhesive layer, adding a water tight seal to the strain relief the tubing provides. When exposed to heat (usually a bit lower than the activation temperature of the heat shrink), the inner layer begins to flow (just like a hot melt glue). When the tubing shrinks and cools down, the inner layer forms an adhesion layer between the tubing and the component or wire. This provides a watertight seal, protecting the connector and/or wire in direct burial and submersed applications. Meets requirements of AMS-DTL-23053/15 (formerly MIL-I-23053/15), Class 1; UL 224 VW-1 flame retardant (jacket only); UL 486D rated for direct burial; dielectric strength 500 V/mil (500 x Jacket Wall thickness x 1000). Crosses to Canusa CFW, 3M HDT, 3M ITCSN, Tyco Raychem RHW, LG PHWT