An accurate way to preset tire reliefs. a constant flow of air to the relief duplicates the air pressure against the relief in the tire. Simply attach air chuck to one end of the gauge and the relief valve hose to the other end. Screw on the back to recalibrate to zero if dropped. Replacement Gauge #ALL44081
Allstar Performance Tire Relief Pre-Setter Gauge - 0-30 PSI ALL44080