SRAM REAR RED ETAP A2 11s 32T MAX BATNOT INCLUpdated version of the original SRAM RED eTap rear derailleur Mechanical necessities such as a carbon pulley cage, ceramic pulley bearings, and anodized alloy artfully blend with proprietary electronic advancements to deliver a shifting wonder Larger X SYNC pulleys and ceramic bearings for increased durability and efficiency Compatible with existing eTap batteries battery not included Orbit chain management technology keeps drivetrain quiet and secure