I have the latest BGC 3" version of the 923007 Random Tech cat and it's 15-3/4" long end to end. That may be meaningless to you because anyone can spec their own lengths.
I had the same cat from 1996 which started to break up internally last year, I'm told due to water getting on the shell when it was hot. I don't think I picked up more than 1-2 psi boost after I helped it break down the rest of the way
Anyway, the later version seems to solve this problem with a sheet of something wrapped around the honeycomb to isolate it from the shell.