I been looking for a piston and notice that there are lots of 9737A pistons but many have a number at the end like --> 9737A 9
some are 9737A 2, 9737A 7, 9737A 8...
what's the difference? Why so many different numbers if they all fit the same thing? My particular application calls for 9737A 9, can I use a 9737A 7???
Slimm