Kingsgrove 15mm Inlet Corner Thermostatic Valve (Pewter)

Each radiator/towel rail requires one valve set as illustrated and priced here.

A thermostatic valve is self-regulating, and controls the temperature of the radiator/towel rail by changing the amount, or flow, of hot water in to the radiator/towel rail. The second type of valve is a manual valve. Simply put, the user rotates or twists the valve to increase or decrease the amount of hot water coming in to the radiator/towel rail.