... unit(mm) 1/4" x 1/4"6.4mm x 6.4mm22,23,243/8" x 3/8"10.6mm x 10.6mm19,20,21 ... ,221/2" x 1/2"12.7mm x 12.7mm16,17,18 ... inch In metric unit(mm) 2" x 3"50mm x 75mm2.0mm,2.5mm,1.65mm3" x 3"75mm x 75mm2.67mm,2.41mm,2.11mm ... ,1.83mm,1.65mm2" x 4"50mm x 100mm2.11mm,2.5mm ...