RockShox Super Deluxe Ultimate Flight Attendant Rear Shock - 185 x 55 mm, C2 Trek Fuel EX 2023+Give your all day trail bike the firepower it needs for rugged terrain, plus the efficiency of an automatic suspension system. Flight Attendant algorithm uses a suite sensors to read rider and terrain inputs to anticipate the perfect suspension position. High flow main piston reduces high speed compression damping, eliminating hang ups and allows the wheel to easily get out of the way on hard impacts. DebonAir+ air springs maximizes fine tuning