I have to comment on the information provided by the link to the site. Residual valves are not there to hold the shoes against the drums. That is wrong. With no residual valve, the master cylinder will pull the fluid back when the pedal is released and the makeup fluid will be in the form of air, entering past the cup in the wheel cylinders. This is very disturbing to see a supplier selling parts with wrong information.

1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed

My Chevy Master 4 Door is on the Road!