This is a brass weight designed to be fastened to the left-rear corner of the chassis, first seen on the 4.8, directly under where your ESC mounts. At just .050" thick and coming in at 0.5oz, this is a great way to place more weight om the left-rear of the car while being as low-profile as possible. Conveniently fastens to the chassis using (2) 4-40 flathead screws; no tape!