VRDL check valves are used to keep a double acting cylinder in its position, in both directions granting the load stop. 3 The valves grant to keep a load in a certain position, they are used with double acting cylinders , to be unlocked they need a pilot pressure. The external body is made of high resistance steel and externally protected from oxidations by zinc treatment. On request we can supply a zinc/nickel treatment to increase the corrosion resistance when the valve has poor protection and it is located in external environments. The sealing is granted by a tapered poppet hardened and grinded.