... (mm) 1/4" x 1/4" 6.4mm x 6.4mm 22,23,24 3/8" x 3/8" 10.6mm x 10.6mm 19,20 ... ,21,22 1/2" x 1/2" 12.7mm x 12.7mm 16 ... metric unit(mm) 2" x 3" 50mm x 75mm 2.0mm,2.5mm,1.65mm 3" x 3" 75mm x 756mm 2.67mm,2 ... ,1.83mm,1.65mm 2" x 4" 50mm x 100mm 2.11mm,2.5mm 4" x 4" 100mm x 100mm 2.0mm,2.5mm ... > In inch In metric unit(mm) 1/2" x 1/2" 12.7mm x 12.7mm 16,17,18,19,20,21 ...