Heavy-duty Type R12H air brake relay valve designed for truck and trailer applications with 2 service and 2 delivery ports; supports quick brake response times and consistent air flow Control port: 1/4" NPT, (2) delivery ports: 1/2" NPT, and (2) supply ports: 3/4" NPT; compatible with standard air brake plumbing in commercial vehicles Crack pressure rated at 4 PSI for precise actuation and reliable braking; rugged internal construction ensures dependable performance in harsh conditions Built with durable components to meet OE standards; direct-fit design supports easy replacement with no modifications required for compatible vehicles Includes (1) air relay valve; matches OE and aftermarket parts like Bendix 103009, Haldex KN28061, Caterpillar 1D-1466, and more; meets brake system performance specs