The MTS Single Pak is the just the basics. It is a combo pack of one MTS Tube™and one MTS Stem™. Customize your Single Pak with the tube size and stem length you want. Each MTS Stem comes with a presta valve core and cap. If you already have MTS Tubes on your bike, there is no need to buy a new MTS Stem. You only need an MTS Tube! Simply unscrew the MTS Stem from your old MTS Tube and reuse it with the new one.