These valves are used for regulating air flow through standard tubing for air controlled devices such as air stones, filters, protein skimmers, ornaments, etc. Also for controlling low pressure liquid feed lines for metering pumps & drip irrigation of water gardens & paludariums. Use teflon tape on threaded fittings for water applications. Made of UV stabilized material. Each fitting is black. Total length of valve is 1 1/2".