This clamp is 11" wide and the center can be expanded up to 5". It is made of sturdy plastic with 4 - 4 5/8" rubber suction cups, a tightening rod and an adjustment wedge to level the seam for less sanding. This is the best of the Seamrite clamps to use for larger seams (kitchens, bars, vanities, etc.).
To enguage the clamp you simply flip the lever. Suctions well to any non-pourous surface. Requires two to do a standard 25" Seam.