HNA 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 a minimum of 60 RC hardness and a depth of 0.125 inches.Each liner is honed to a mirror-like finish for smooth and even wear during the life of the liner and is machined to close tolerances to assure easy installation and long life.