Grips sheet until release ring is pulled. Serrated gripper is hardened tool steel. Forged head and gear. Safety factor is 2 to 1. Power coated finish. Designed to meet ASME B30.20 standards. Do not use plate clamps to lift loads less than 20 percent of rated capacity. Lift only one plate at a time. Plate must be clean and free of oil. 800 lbs Plate weight. Not designed to use on stainless steel or aluminum plates. For use with materials with a surface hardness to 30 RC (300 HB).