The Osprey Spare Sternum Magnets are used along with the magnetic bite valve to ensure water flow is easy and quick to access. You can have them on many bags and tranfer from bag to bag or just have extras as spares for when you need them. The Osprey Spare Sternum Magnet Pack of 3 features Pack of three Detachable Sternum Strap Magnet A spare magnet for use with the Osprey Hydraulics™ on any existing Osprey pack. More info