The Extra Valve is an additional valve for your existing Orbit Complete Yard Watering Kit with part numbers 58872 and 91591. This easily turns your 4-station yard sprinkling system into a 5-station sprinkling system. Designed so you can mount your Orbit Hose Faucet Timer to the front of the valve. Built with high-quality materials and waterproof construction, so you can count on many years of dependable use.