Initially developed for our ATV shock conversion kits made in 2004, we set out to develop the best adjustable shock under 250. After years of feedback and improvements, we are happy to provide a shock that can be used on ATVs, Motorcycles, and other off-road vehicles to upgrade stock suspension performance. Compatible with our Adult ATV Shock Conversion Kits. (Same size as 400ex stock shocks) These shocks are adjustable in length, spring preload, and rebound: Length can be adjusted by unscrewing the lower shock eye, and threading nut to desired length. Preload can be adjusted using included tool to tighten the nut/collar above spring coils. Rebound can be adjusted by twisting the knob near the lower shock eye 0-24 clicks. Coil Size: 9mm