The Seam Weight has a perforated white plastic base with an air space between the base and steel weight to allow heat and moisture to quickly dissipate. It performs better than a tool box tray because it exerts uniform pressure without discoloration caused by heat retention or by a rusty tool box tray. The white plastic base glides smoothly over the carpet and won’t snag like a plywood base or tool box tray can. Can be used on seams made with 3" or 6" wide hot melt tape. Measures 6" wide x 12" long x 3-1/4" high. Weighs 16 lbs.