2:1 Shrink Ratio, Flexible, Flame Retardant, Polyolefin Tubing 0.750 (3/4) inch Red 4 FT Length MIL-DTL-23053/5 C3 is a flexible, flame retardant heat shrinkable polyolefin tube. It is designed for a wide range of applications requiring high heat-resistance, including insulation for electric & electronic devices, wire strain relief and protective covering for parts such as resistors and capacitors.