Expansion PEX tubing is cross-linked, high-density polyethylene. It’s 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 as well as hydronic radiant heating systems. PEX tubing can also be used in continuously recirculating plumbing systems up to 140° F while maintaining chlorine resistance.