... ,17,18,19 1" x 2" 25.4mm x 50.8mm 14,15,16 2" x 2" 50.8mm x 50.8mm 12,13 ... 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 ... ) 1/2" x 1/2" 12.7mm x 12.7mm 16,17,18,19,20,21 3/4" x 3/4" 19mm x 19mm 16,17 ... ,18,19,20,21 1" x 1" 25.4mm x 25.4mm 15,16 ...