... are the 12 tooth, 16, 18, 20, 24, 32, 36, 40, 48, 50, 60 Tooth 3.175mm, 4mm, 5mm, 6 ... the shaft of most of NEMA23 Motors.2gt pulley 40 tooth 5mm 6.35mm 8mm 10mm boreTooth Profie: GT2Tooth ... profile timing pulley similar with S2M Pulley.GT2 Pulley 36 Teeth 5mm 6.35mm 8mm Bore36 Tooth GT2 Pulley ... is too Thin.)Timing Pulley Coupling 2GT 40 ToothGT2 tooth profile 40 tooth Timing Pulley with M8 screw bore ...