I finally got around to fitting my TPU tubes yesterday. Or at least, I tried to. I encountered a problem that's brand new to me: the valve stem, which is smooth plastic, was marginally too large a diameter to fit in the valve hole in the rim. It's definitely not just an overhang of tape, as I tried it from the inside out, so to speak, to make sure. And I'm sure it's the valves being out of spec not the rims, as I've never had this problem before, with any brand of tube. I suppose I should have tried the other tube just to make sure (I only intended to fit one, just to see how they held air etc) but I didn't. I guess I'll have to try and return them via Ebay. Gustavo brand, purple colour in a yellow box, for you to avoid.