SRAM Apex XPLR AXS Rear Derailleur - 12-Speed 44t Max Battery Not Included BLK D1SRAM Apex XPLR AXS Rear Derailleur 12 Speed 44t Max (Battery Not Included) Black D1. The SRAM Apex XPLR AXS rear derailleur fits wide range cassettes with 36t or 44t large cogs and incorporates a spring clutch for flawless chain management on or off road. Innovative and intuitive eTap shift logic and AXS connectivity keeps Apex delightfully distraction free. SRAM AXS enabled for easy setup personalization and reliability 1x specific for use with SRAM