Oil Flow Control Valves include Sight Feed Valves, Solenoid Valves, and Precision Relief Valves.  Sight Feed Valves allow visual observation of the liquid stream, with the volume of flow controlled by an adjustable needle valve. These units are principally used on gravity or pressure lubricating systems.  Their use can be extended to any application requiring adjustable, visible flow control. Solenoid Valves are for use with electrically operated mechanisms, and precision relief valves are used as a safety device on reservoirs where a certain maximum pressure should not be exceeded.