Is it possible to rebuild a brake booster ? Do they

I had the 7 inch booster rebuilt by Stewart,s in Stoney Creek,Ontario.This was for my 68 Barracuda and they got the parts(diaphram)from Cali.
Thanks , booster and MC off to John Stuarts , expensive , but at least they can do the job . Will have SS sleeves put in the master , they say 4-6 years for a regular rebuild should last as long as the car with SS sleeves in it .
Thanks again, will be good to have solid brakes again.