Black 1/4 inch HSPO Heat Shrink Tubing with 100 ft, thin wall, flame retardant, 2:1 shrink ratio, flexible, cross-linked polyolefin heat shrinkable tubing. HSPO thin wall, heat shrinkable tubing is a general purpose heat shrink tubing made from a specially formulated, cross-linked polyolefin. It offers excellent electrical, chemical, and physical properties. This tough, flexible tubing can be used for insulation, harnessing, strain relief, and identification purposes in a variety of industrial and military applications.