Got some wheels recently, sans valve stems.
"No worries" I thought - "I'll get some Stans, they're apparently compatible"
Well, it appears that they aren't - certainly not the UST versions I bought. There's a large gap between the seal at the end of the stem and the rim where the rim 'arches' towards the top (imagine the rim profile as an inverted 'U' - the Stans valves sit happily on the sides of the 'U' but do not have enough depth to also seal the top).
Short of finding some Shimano 'valve units', what else is there out there that will work?

