. This is heat shrink tubing that has been designed to shrink up to 1/2 of its original size with the use of a heat gun, lighter, soldering iron, etc. It's ideal for insulating electrical splices, and covering electrical plugs and connectors, plus it has many other uses. They come packaged in 3" lengths. They have a 1/16" diameter, is blue in color, and come 4/pkg.