Gripping Cams Dual serrated gripping cams clamp onto the plate for a more secure lift and are rated for material with a surface hardess of up to 420 Brinell High Strength Shock... Resistant Steel Provides for longer clamp life. Rated for 420 Brinell Surface Hardness Grippers are rated to lift material with a surface hardness of up to 420 Brinell. Available... with smooth gripping surface of bronze or stainless steel for handling plate with a surface hardness in excess of 420 Brinell and polished metals. As top sling angle increases...