Centric caliper - which model is this for?
 

I purchased a rebuilt Centric caliper number 141.37551 for a 69 912 rear brake. However the pistons are different from what came off the 912. My 912 rear pistons are not hollow like on the rebuilt (see picture). Can anyone tell by looking at the pistons which Porsche model this will work with?http://forums.pelicanparts.com/uploa...1345823436.jpg

That should work fine, it just has the later 'inverted' style pistons. Functionally equivalent. Without the spacer for vented rotors, it has a very limited application; probably 1969 912 and 1976 912E and a few 1969 to 1973 911T with solid rotors..

Measure the old piston diameter and the new piston diameter. If they are the same, don't worry about the hollow vs. non-hollow. Note that you need to extend the piston out a bit to ensure you're measuring the correct part of the piston- the clean area that seals the fluid in the caliper.

The hollow pistons are stepped on the end to prevent pad noise. This is the step that you have to set at the 20 degree angle. The hollow pistons also have less thermal mass to reduce heat transfer into the caliper. So in theory the hollow pistons are better.