IRWIN Vise-Grip Locking C-Clamps reach into places where ordinary clamps cannot be used. Swivel pads are fitted to prevent damage to soft materials and are designed to hold irregular or tapered work. Hex key adjusting screw that tightens to draw materials closer together and also provides controlled release. Visegrip Irwin 18SP Locking C-Clamp Swivel Pad. Length: 450mm (18in). Throat Diameter: 240mm (9 1/2in). Capacity: 203mm (8in).