These DSX original fittings are made from 6061 and then anodized black and laser engraved. They make connecting two male GM push connect ends a snap. Unlike other fittings out there that use difficult to deal with backing nuts, this uses stainless steel snap clips inside as well as a double fluorosilicone o-ring seal on each end to provide the easiest installation coupled with leak free operation on even the worst of fluids.