Today's aerodynamic rims often need an extra long valve, and it can be tough to find a tube with an 80mm valve stem!. These valve extenders work with any presta valve by simply threading over the top. They come in two length options - 48 and 72mm, for use with our 56mm and 86mm carbon clincher wheelsets. The 40mm wheelsets can use a standard 60mm valve and should not require and extender. This price is for a set of two extenders, but you will receive the appropriate set of valve extenders for free with any carbon clincher wheelset purchase!