Earl's Perform-O-Flex stainless braid-protected synthetic rubber hose is the premium quality racing hose depended on by the top racing teams of every professional sanctioning body in the world. Perform-O-Flex features an inner liner of synthetic rubber. A partial coverage protective sheath of stainless steel braid is embedded in the liner during manufacturing. The reinforced hose liner is then bonded to a full-coverage outer protective sheath of high tensile stainless steel wire braid. Tougher than this, hose doesn't get. Yet Perform-O-Flex, with its inner liner, remains flexible at temperatures between -40 and +350 degrees F. Racing Greats have depended on Perform-O-Flex hose and Swivel-Seal hose ends since 1972. Perform-O-Flex hose is intended for use with Swivel-Seal, Auto-Fit and Auto-Crimp hose ends only. No other Earl's hose ends are intended for use with Perform-O-Flex hose. The use of other manufacturer's hose ends is not recommended. PSI rating is determined by many factors including hose end in use and assembly method.