Specification:Name: Chain Drive SprocketModel: 08BMaterial: A3 SteelSurface Treatment: Hardening of teeth surfacesTeeth Pitch: 12.7mmTeeth: 10 Teeth ~ 21 Teeth08B Sprocket Can be Used with 08B, 428 ChainNote:1.The center is the method hole, need clients to purchase again their very own processing to expand.2.The length of the process holes may well range from batch to batch. If you've got requirements for the dimensions of the process hole, please seek the advice of customer service for the actual size.3.Due to the batch of other step diameter will even vary, please be successful in kind.Package :Packing : Plastic bag / Carton box.Quantity : According on your Choose!