The Rexroth R900599536 SL20PA2-4X/M is a high-performance logic cover featuring an integrated pilot-operated check valve function. Designed for installation within block designs, this component ensures reliable and leak-free blocking of flow in one direction. Flow is permitted from port B to A, while the reverse path is securely closed until a sufficient pilot pressure is applied at port X to open the valve. This particular model from the 4X series is a size 20 valve, includes a measuring port for pilot pressure (/M), and is built for durability and precision in demanding industrial hydraulic systems.