PEX Tubing Comparisons PEX-A PEX-B PEX-C Compared! HousePEX PEX-A & PEX-C Tubing Techs / Specs / Benefits. HousePEX PEX-A tubing is crosslinked using peroxide crosslinking, a so called PEX-a process. By means of heat, a peroxide mixed into the PE raw material is split into radicals. These radicals react with the PE polymer chain and absorb hydrogen atoms to become inert. The polymer chains now becomes radicals.