if u ever rebiuld your rear brake piston and find it pitted or rusty heres a easy fix to smooth it out.
get ahold of a cordless drill
get 2000 grit wet or dry sand paper
a can of wd-40
put the piston in the chuck of the drill,dont over tighten it or it will mar the skinny end and you will hav a leaker.
spay the piston with the wd-40,and also the sand paper.
start at a slow speed and keep it wet.takes a few minutes and it will look like new.
its like a getto lathe!