It's hit and miss for these deep chin splitters :-/
The genuine items are made from polypropylene plastic like you said, im sure of it.
The one in the link is quite cheap, I wouldn't know if it's any good. I had a cheap one from eBay a while back, was in a JOM packaging, didn't fit well at all and kept popping off but was flexible.
See where it says "1 Sold" .. Well that was me 
My car is proper low and will be even lower on the BBS's, so it will take a battering for sure.
I'll report back when it's broken 
See where it says "1 Sold" .. Well that was me 
My car is proper low and will be even lower on the BBS's, so it will take a battering for sure.
I'll report back when it's broken 
Hang on what about your US splitter?!!?!