Size 3-1/4" Weight 6.50 Max. Opening 3-1/4" Min. Opening 0" Depth 2-1/2" Screw Dia. 7/8" Test Load 16,250 Lbs. Weight Per Box 6-1/2 Lbs. Frame is forged from high-strength, heat-treated steel. Large diameter screws are full length and hardened to prevent bending and protect threads. Clamp strengths exceed test loads shown. Conforms to Federal Specification GGG-C-406D, Type 1, Class B, heavy service.