De Luxe forged hand controls feature a smooth and compact design, and are just perfect for any old school project. Brake master cylinder features forged aluminum body and clamp, forged brass finned master cylinder lid and forged brass lever for a true old school look! Brake master cylinder has a 9/16 bore and can be used with single 2-piston caliper, 4-piston caliper, 6-piston caliper or dual 2-piston calipers. For 1″ diameter handlebars. NOTE: we suggest to use DOT 4 brake fluid. in any case do not use silicon based oils.