1/2 and 1/4 inch Floating Valve Assemblies control the water/nutrient solution level in the primary reservoir (controller). comes with 1/2" brass barbed fitting. 1/4 float valves have a short stem and connect to 1/4in tubing and are perfect for hooking up to Reverse Osmosis Systems. Long stem 1/2 float valves attach to 1/2in tubing and are used for maintaining reservoir levels in hydroponics systems.