Pipes uses the Puffer mold. He looks great, though is not accurate. You can read his entry on TFWiki for details. I can only half make sense of it. He has a new head sculpt, that like his paint job, is also not completely accurate.
Overall: Pipes is probably, strictly speaking, not a must have, but we aren’t likely to get another Pipes anytime soon, so he’s one you probably want to pick up.
Thanks for reading!