SHIMANO ALFINE - Double Pulley - Chain Tensioner Perfect for SHIMANO ALFINE equipped bicycles, the double pulley chain tensioner can accommodate a front chainring difference of 16 teeth and sprockets sized 18 to 20 teeth. PRODUCT SPECIFICATIONS - MODEL NO CT-S500 - SERIES ALFINE S7000/S700 Series - Color Silver | Black - Compatible cassette sprocket CS-S500 - Max. rear sprocket 20T - Min. rear sprocket 18T - Dropout Vertical drop end type - Structure Double pulley - Compatible chain HG 9-speed - Max. front difference 16T - Rear speeds Single