Replacement chainwheel for your Bafang BBS01 or BBS02. Replacement sprockets in either 44, 46, 48, and 52 teeth. 

52 tooth gives you super high gearing for high speed (recommended for on road use only)

48 tooth is right in between and is the standard chainwheel that Bafang ships the units with

46 tooth sprocket give you better hill climbing ability (great for off road)

44 tooth sprocket is best for big 29er wheels and steep hills

Unless you want maximum top speed we recommend the 44T for better torque and greater longevity from your drive unit.