... bore hardness not less than 63HRC 3.API standar Hardened liners Hardened liners offer economy in a liner that is made for ... normal to mildly corrosive mud conditions.These liners are hardened and heat treated under strict quality control to ... Petroleum Machinery for Emsco, National, Oil well, etc mud pump liners.BrandmodelemscoF-350F-500F-650F-800F-1000FA-1300FB-1300FA-1600FB-1600gardener ...