The Black Diamond 1/4"-28 SAE 90° Grease Fittings are built for dependable lubrication in demanding applications, with a 90° profile that improves access and a 6,000 PSI working pressure. With IATF 16949 approved manufacturing, each fitting is heat treated to SAE J534 specification, with the greasing end hardened to a minimum of 83 on the Rockwell 15N scale and a case depth of 0.005" to 0.009" for wear resistance. A ball check with heat-treated springs helps maintain a consistent seal and extended service life. These steel fittings are zinc plated for corrosion protection, and profile and dimensions are tightly controlled to conform to SAE standards.