Product Name: 0.5 Modules Plastic Gear Crown Gears Material: Plastic Modules: 0.5 Modules Model: C152A, C203A, C282A, C282.5A, C303A, C322A, C20082A, C28082B, C28102.5B Thickness: 4-5mm Gear Diameter Calculation Formula: (number of tooth + 2) X 0.5 (mm) C152A: External Teeth: 15 Teeth, Bore: 1.95mm, Tight fit 2mm shaft C203A: External Teeth: 20 Teeth, Bore: 2.95mm, Tight match 3mm shaft C282A: External Teeth: 28 Teeth, Bore: 1.95mm, Tight match 2mm shaft C282.5A: External Teeth: 28 Teeth, Bore: 2.45mm, Tight match 2.5mm shaft C303A: External Teeth: 30 Teeth, Bore: 2.95mm, Tight fit 3mm shaft C322A: External Teeth: 32 Teeth, Bore: 1.95mm, Tight fit 2mm shaft C20082A: External Teeth: 20 Teeth, Internal Teeth: eight Teeth, Bore: 1.95mm, Tight match 2mm shaft C28082B: External Teeth: 28 Teeth, Internal Teeth: eight Teeth, Bore: 2.05mm, Loose match 2mm shaft C28102.5B: External Teeth: 28 Teeth, Internal Teeth: 10 Teeth, Bore: 2.55mm, Loose fit 2.5mm shaft Pack Quantity: 20Pcs