RockShox Super Deluxe Ultimate D1 Rear shock 230x57.5 Shaft Eyelet: Standard Body Eyelet: Standard Token Loc 0 Reb55/Comp37 Lockout45 Trek Rail Gen4 2020-2024LinearXL air spring with easy to adjust "o ring" tokens RCT2 damper providing a wide, usable range of Low Speed Compression (LSC) and High Speed Compression (HSC) adjustments without any cross talk Base valve with 40% reduction in IFP forces, making it the most supple shock on the market while maintaining perfect traction Main piston compression tunes matched in performance to the Charger 3. 2 damper, focused on providing mid stroke support Jounce