RD-M21SSA SUPER SHORT CAGE (6/7 SPEEDS) - Model No.:RD-M21SSA - Cassette Compatibility: 6 / 7 Speed - Cage Type: Super Short Cage - Front Chainring:Single - Max. Sprocket: 32T - Min. Sprocket:11T - Total Capacity: 21T - Guide Pulley: Engineering Composite with Steel Bushing - Tension Pulley: Engineering Composite with Steel Bushing - Bracket Body:Resin / Black - Mount Type: Reverse Bracket Type - Bracket Pivot Seal: NO - Plate Body: Resin / Black - Plate Pivot Seal: N - Outer Link: Resin Steel - Inner Link: Black Steel - Link Pin Bushing: N - Outer/inner Plate: Black Painted Steel - Weight: 241g - Compatibility: Shimano 6 / 7 Speed Rear Derailleur