Engineered to replace Haldex FF-2 trailer brake valves, World American SSA KN28601 features full function operation with 4 delivery and 2 spring brake ports for optimal air control in heavy-duty trailers. Built with 3/8" NPT delivery and supply ports, 3/8" spring brake ports, and a 3/8" reservoir port. Control port: 1/4", total of 4 delivery and 2 spring brake ports for reliable trailer control. Cracking pressure set at 3 PSI for responsive air braking. Durable, high-performance design with NPT threading ensures universal compatibility and easy installation. Manufactured for use in full function air brake systems. Ideal for heavy-duty trailer applications including Utility, Mack, Volvo, Freightliner, and more. Replaces over 30 OE and aftermarket part numbers including Haldex KN28601, Meritor R955KN28601X, Automann 170.KN28601, Genuine Newstar S-22188, and Tectran TV28601.