I have 01 A4 B5 and I'm trying to make a list of items that I will need to fix the bumper. I'm also not sure what material is this OEM bumper made out of and I don't really want to take it off just to check. Any recommendations of how to fix the crack/dents and which particular materials to use? (I got the painting part covered)

Pic: Bumper

 

I believe it's ABS plastic, but you could always use finishing putty or body filler.

 

It's ABS, to fix a crack like that and make it last you'd probably have to plastic weld it, or at the very least fiberglass the crap out of it at the back and hope for the best.

 

I went from a nasty gash (never park near the entrance to a lot where people are dragging boats in and out on trailers) to a pretty cheap fix using Bondo glazing putty. But that crack is a real structural problem on a piece that's always going to be flexable. I think you're in trouble on that one.