These assemblies are set up to take the master cylinder directly, or they can also be used with a small vacuum booster mounted in between the master cylinder and the master cylinder mounting plate. I have found out that they can also be used with a "remote fill" unit that mounts in a more exposed location, so that you don't have to perform a Houdini act to add fluid to the master cylinder (which will be hidden up under the dash). This is a very well thought out design, and if I had known more about them at the time I built my roadster pickup, I might have either purchased the one shown or attempted to build my own. However, I will point out that building one of these units is not for the faint of heart----There is a lot of machining and precision fitting necessary to make one of these units work correctly, and a failure of any part of it could have some very horrific consequences for the builder/user.