Our 4:1 heat shrink tubing is also available with a "dual-wall" construction. 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.