Solid aluminum extruded square will not bend or break. Aluminum will not rust or corrode. Stamped conversion tables. Thick edge makes for a safer saw guide. No. 2990: Size: 7 In., Graduations: 1/8 In., Material: Aluminum, Pkg Qty: 1, Package Type: Card No. 2990G: Size: 7 In., Graduations: 1/8 In., Material: Aluminum, Pkg Qty: 2, Package Type: Card