Expansion PEX tubing is cross-linked, high-density polyethylene. Its available in white, red, or blue colors for easy identification of hot and cold water lines. The Apollo Expansion PEX tubing listed is type PEX-A (PEX-a, PEXa). PEX tubing is for use in hot and cold potable water distribution systems. PEX tubing can also be used in continuously recirculating plumbing systems up to 140 F while maintaining chlorine resistance.