Spring Tower Frame Plug Kit for JL JT and JK Frames. CNC Machined Black Delrin RockJock 4x4RockJock's JL JT JK Front Spring Tower Plugs are a simple, easy to install detail part that help to cleanly finish off a nice build. As axles get wider and aftermarket fenders get installed, these areas of your vehicle become more visible. Clean it up with these and other frame plugs from RockJock! Additionally, in many wheeling applications, when vehicles are subjected to being submerged in water and mud often, the spring towers can fill up from the