When used on presta drilled rims valve hole diameter 65mm the rubber valve base ensures a perfect air tightness simply tightening the valve on the rim with its nut without any additional adapter when used on presta drilled with a wider 65mm inside hole or when used on schrader drilled rims valve hole diameter 85mm effetto recommend fitting the conic adapter on the valve before inserting it into the rim use the metal washer on the outside of the rim before tightening the val