... (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 ... 16,17,18,19,20,21,22,23 5/8" x 5/8" 16mm x 16mm 18,19,20,21, 3 ... /4" x 3/4" 19.1mm x 19.1mm 16,17 ... ,18,19,20,21 1" x 1/2" 25.4mm x 12.7mm ...