Fluidmaster recommends using the 400A fill valve in toilets that date prior to 1994 with flush volumes between 3.5 and 7 gallons per flush. Fluidmaster’s 400A Universal Toilet Fill Valve is the #1 best-selling 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. Does not replace Side Entry Valves. For best performance of your toilet, consider replacing the flapper along with the fill valve. Fluidmaster® recommends the 400CR Repair Kit that has both the 400A fill valve as well as the 2 inch 501 flapper