Ratcheting Aluminum Dual 4-1/2" Cup Horizontal Seam Setter designed for pulling together flat, smooth sheets of material exactly to the millimeter. Vacuum for the seaming tool is produced by pressing down the levers on the two (2) 4-1/2" cups. Constructed from high density aluminum alloy with ABS ball handle knob. Suitable for all materials with plane like glass, plastic, metal, wood, marble, etc. Typically, one setter is required for every two feet of material edge to be seamed.