Longacre Digital Air Density GaugeAir Density (or RAD relative air density) is a valuable tuning tool to make sure your jetting is at its optimum. Longacre's Digital Air Density Gauge helps accurately measure your air density with an easy to read digital display. The gauge records your baseline for future reference. If the air density changes (and it will), a Red LED flashes to let you know to change jets (alarm with + 5% change). The compact gauge also shows the current temperature