The Thumb Valve is spring operated for easy on/off control: press to open and release to close. It has a narrower passage than the Aluminum Shut-Off-Valve and can be paired with the 170 Water Breaker, Seedling Nozzle and the Fogg-It Nozzle. Made from die-cast aluminum and zinc. Chrome plated. 3/4" fht x 3/4" mht.