Superior Engineering rear coil retainers are used to hold the bottom of the coil down on the diff. They are sold in pairs, one for each side. When combined with the Superior coil drop out cones, a longer shock can be used which will give the vehicle more down travel. Caution must be used not to use to large a shock as the shock may "bottom out" on compression. Using Superior coil retainers is also a safer setup as it eliminates the chance of a coil ever coming out from under the vehicle and causing injury.