Heavy-duty air brake relay emergency valve with 3 PSI cracking pressure and charging style design, suitable for commercial truck and trailer applications. Ports: 1/4" control, 4x 1/4" delivery (0.375" dia), 1/4" emergency, 3/4" reservoir with nipple, 0.25" service, 1/4" supply/emergency, NPT threading. Delivers reliable performance in emergency air brake activation; reservoir port provides added volume for safe operation. Meets OE specifications with consistent delivery and response pressures (4.5 ± 1 PSI crack pressure); built for long service life. Replaces OE & aftermarket parts: Haldex, Meritor, Bendix, Freightliner, Tectran, Automann, Euclid, Velvac, Wagner, and more (see full list below).