https://www.fluidmaster.com/toilet/part-type/toilet-fill-valves/ Toilet fill valves refill the toilet tank and bowl to the correct water levels after flushing. Fluidmaster invented the fill valve technology in 1957 and is the largest selling brand of fill valves. The 400H PerforMAX Toilet Fill Valve has been specifically designed to boost your toilet’s performance, providing a consistent and reliable flush. Say goodbye to the frustration of weak flushes and hello to a cleaner and more efficient toilet.