Fluidmaster recommends using the 400A fill valve in toilets that date prior to 1994 with flush volumes between 3.5 and 7 gal per flush. Fluidmaster's 400A universal toilet fill valve is the No 1 fill valve in the world. A universal design, with an adjustable height from 9 to 14 to fit most toilets. The 400A offers quick refill rates and replaces ballcocks and other toilet fill valves. A trusted and proven toilet fill valve, the 400A is built to last from corrosion-resistant materials for a long lifespan. This code approved, anti-siphon design, won't contaminate the fresh water supply. Some toilet models not supported - Glacier Bay or Niagara flapperless toilets, one-piece toilets.