A high quality material which shrinks to 1/3 its size.  Polyolefin is stable, and can be stored for extended periods of time without shrinkage.  It remains flame retardant, and is very flexible.  When heated, the sealant flows and physically encapsulates, creating a waterproof connection.  Available in the following diameters:  1/8", 1/4", 3/8",1/2", 3/4", 1", and 1 1/2".