The gauge gives you a reading while you're actively pumping. Once you stop pumping the valve's sealing surface closes and the gauge is no longer in contact with the chamber's pressure.
|Action:||Inflate and deflate|
|Pump Dimensions:||2.75" Dia. x 25" H|
|Chamber Dimensions:||2.75" Dia. x 18.5" H|
|Hose Length:|| 48"|