Blichmann G2 Linear Flow Valve
The G2 Linear Flow Valve from Blichmann Engineering allows you to have precision control over your liquid flow rates when sparging, lautering, recirculating in a RIMS system, or when used with a wort chiller.
It is easy to disassemble for cleaning, and the 'globe valve' allows far more precise control of the flow rate than a typical ball valve.
Simply adjust how far the two parts are threaded together to control your flow rate. (1/4 of the way open is 1/4 of the total flow, 1/2 is 1/2, etc.)
It even has a convenient silicone grip to aid in adjusting it when hot.