1Pcs 45 Degree Helical Gear 1 Mod 12 Teeth-20 Teeth Right Rotation Gear 45# Steel Blackened Round Bore & Keyway Bore & D BoreName: 1Module Helical GearMaterial: 45#SteelTeeth: 12 Teeth - 20 TeethBore: Round Bore & Keyway Bore & D Boree.g:16mm keyway 5x2.3mm,means Round Bore=16mm,Keyway Bore width=5mm,Keyway Bore depth=2.3mm. D Bore 10x9mm,means D Bore width=10mm,D Bore depth=9mm.