High-quality grey iron is cast and machined to very close tolerances. Withstands distortion under high pressure. Swivel base for easy positioning. Smooth, dependable action from long barreled, unbreakable nut dovetailed into body. Aligned main screw and nut reduces wear for long service. Designed for professional woodworker/metal workers; provides more than 3000 pounds of clamping pressure for heavy duty jobs. Fused steel handle with 2 1/2-inch throat depth and 4 1/4-inch clamping capacity. Safety stop prevents slide from separating from body. Anvil incorporated. 4" (100mm) without Swivel Base The jaws, handle and main screw are steel, the latter having a two-start rolled acme thread to speed the jaws from fully closed to fully open with a minimum of winding.