4", Light Duty, U-Style Bar Clamp, Rail Is Made Of Quality Steel Drawn In A Single Piece For Durability & Strength, Sliding Arm Is Made Of Die Cast Zinc Which Is Light, Stable & Break Resistant, U-Shaped Rail Enables Step Over Clamping For Those Hard To Reach Spaces, Plastic Pressure Caps On The Top & Bottom Sections Protect The Work Piece Surface, 4" Clamping Capacity, 2" Throat Depth, 330 LB Clamping Force.