CeramicSpeed SRAM Red XPLR OSPW X System. Features: Further Drive Technology aimed at making the OSPW X boost the XPLR group's ability to perform efficiently over time Active Debris Remover (ADR) features a unique new dust cover that sits safely anchored in a recess in the pulley wheel, completely enclosing the bearing. This is paired with a bladed groove structure that surrounds the dust cover, and dynamically extracts debris from the pulley wheel while it's rotating ADR is paired with new 14-tooth and 20-tooth solid disc pulley wheels, simply known as the ALPHA The ALPHA Disc features two-piece construction: narrow-wide tooth profile composite material offers prolonged wear protection and noise reduction. Solid aluminum disc eliminates the potential of external objects getting stuck between the spokes of the pulley wheel, while adding strength and stiffness Specs: Model:Standard Compatibility:SRAM Red XPLR E1 Upper Lower:14/20t Color:Black