Throttles type ED, RD, and RDF are flow valves. They are used in hydraulic circuits to control the flow of single and double acting actuators. The two smaller sizes (type ED and RD) are a combination of slotted and annular gap design to improve adjustability. The larger sizes feature an annular gap design only. The restrictor check valves type RDF make use of an orifice for throttling. A shim, which is very sensitive to the slightest flow, functions as the check valve in restrictor check valves type RD and RDF. The type ED valves are pure throttles.