Aluminum, split barrel bushings come in eight different hole sizes and one, special, pre-machined bushing to make this universal Barrel Vise system the very first choice of professional gunsmit hs. Steel Bushings provide years of service, plus have the necessary clamping power to break loose the tightest barrels. Aluminium Bushings give exceptional holding ability without marking your barrel. Solid Bushings - Solid bushings that have NOT been split so you can alter them as you want.