The Campbell Hausfeld ST128407AV Pilot Unloader Valve is a 1/2-inch port unloader valve rated for 95–125 PSI, designed to vent pressure from the compressor head during unload cycles so the motor can restart without load. The ST128407AV designation identifies this exact Campbell Hausfeld part, and retailer listings confirm it as the ST128407AV pilot/unloader valve used on Campbell Hausfeld air compressors requiring a 1/2" connection.
