Pressure compensated priority flow dividers similar in function to the popular RD-100 flow controls. The adjustment on the RD-500's is set by a screw, then locked in place to maintain the setting. Maximum inlet flow is 30 GPM, priority outlet flow is adjustable from 2-12 GPM. Priority outlet flow stays constant, excess port takes whatever is left. EF port can be routed to tank, or to a 2nd curcuit. Often used to divide off a circuit for power steering (CF port), using the EF port flow for other uses.