I ordered a bunch of OPP self stick bags from 
Heiko a while back, and I've still got the 
little labels that give the item number on 
them.  Here's the info for the bags I currently 
use:

T24.5-30 (the "standard" size cel bag you 
usually see)

T-B4 (longer and a bit taller than the bags 
above, I use these for movie-sized cels)

T38-60 (these are really big suckers that I use 
for large pan cels, folding over or cutting off 
the part I don't need)



Hope this helps!

-Pasiphae