I have a blue plastic Cobra fender (right side) left over from when
its mate was taken out by a piece of tire tread lying on the freeway
the first year I owned the trailer (1982). I bought galvanized steel
fenders from Northern Hydraulics (now Northern Tool). They were nearly
a bolt on (had to redrill one or two holes) and would still look good
today except for:

1. My trailer sits outside leaning at a slight angle. The fender on
the low side catches the runoff from the roof and has a rust streak as
a result. Unsightly, not structural.
2. Two years ago I blew a tire dramatically and, as another poster
similarly reported, it bent the rear few inches back in on itself. I
banged it out and may even one day smooth it off and paint it, but
it's servicable.

If I had it to do over again: metal. No question about it.

Chip Bearden
ASW 24 "JB"
USA