Info:Martin 10B17 Metric Stock Bore Solid Type B Simplex Roller Chain Sprocket, 12 to 47 mm Dia Bore, 96.079 mm OD, 10B-1 Chain, 17 Teeth, 15.875 mm Pitch, Steel
Info:Martin 10B20 Type B Single Strand Solid Stock Bore Roller Chain Sprocket, 16 to 51 mm Dia Bore, 111.164 mm OD, #10B-1 Chain, 20 Teeth, 15.875 mm Pitch, Steel