Gray Presta Valve Core Extender GRAYs newest custom-designed valve extensions are now designed for "inline" use Inline extensions are installed between your existing valve stem and the Presta valve core, creating a more reliable seal. A rubber o-ring at the base of the extension prevents leaks. Inline valve extenders can only be used with Presta valves which feature a removable valve core. For easy core removable and installation. Available in two lengths (40mm and 80mm). Compatible with all carbon wheels. 40 mm for 5.0 and 45WLX, 45WLC wheelset / 80 mm for 9.5 and 80WLC wheelsets.