These Vittoria value extenders allow standard length valve stem tubes and tubulars to be used with deep section rims. The Vittoria presta valve extenders require an inner tube or tubular with a removable valve core. These extenders are well designed and seal quite well without the use of Teflon tape or thread sealant. Vittoria provides an invaluable little tool is used to tighten the extender and that fits over the valve and down onto the flat section of any removable presta valve core. These can be very handy to carry in your saddle bag or in a tube repair kit. Valve cores have a funny way of getting loose over time.