RD-M21SA (6/7 SP) SHORT CAGE - Rear derailleur. - Mountain bikes. - Model No.: RD-M21SA. - Cassette Compatibility: 6 / 7 Speed. - Cage Type: Short Cage. - Front Chain ring: Double. - Max. Sprocket: 32T. - Min. Sprocket: 11T. - Total Capacity: 37T. - 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: No. - Outer Link: Resin Steel. - Inner Link: Black Steel. - Link Pin Bushing: No. - Outer Plate: Black Painted Steel. - Inner Plate: Black Painted Steel. - Weight: 269g. - Compatibility: Shimano 6 / 7 Speed MTB Rear Derailleur Compatible.