Valve stems are a necessary part to keeping air in your tires, so you can ride the trails safe. If you have your bike set up for tubeless tires, valve stems are a separate component for your tires. If you have tubes in your tires, then the valve stem is included in your tire tube. Valve stems come in two different styles. Either Schrader “which is the same style as your vehicle tires” or Presta, which is used with most tubeless setups.