Well, Foster's is more like 22 minutes, but you're right, 175MB is the standard fro pretty much every other show I've downloaded, so it's weird that this one is so big. To be honest, I was a little wary of it at first, because I've been downloading the complete Teen Titans recently, and whilst most of those are 175MB, there were a couple of episodes that were much bigger that just didn't work.
I can testify that this one works though, and that the quality's great.