The stan39s notubes universal valve stem has been designed with a removable valve core so you can inflate your tyres easier to install the valve stems simply temove the included valve and nut and insert the valve through the rim then thread the nut on to the valve and tighten by hand the valve stems are sold in pairs and they are available for both road and mountain bike rims they are compatbile with tubeless and non tubeless rims but you must have the correct conversion kit f