Pilot operated check valve is designed to lock a cylinder or part of a circuit while a control valve is in neutral position. Double internally pilot operated. Holds circuit at desired pressure while in transport or working. Eliminates replacing worn spools and old valves. Rugged construction; made of high strength anodized aluminum with hardened and ground ball seats. Applications include loaders, outriggers, back-hoes, work platforms and cranes. Rated at 15 GPM, 3,000 PSI. Semi-adjustable, with 1/2in. port pipe thread. U.S.A.