Aqua Plumb 5612 Flapper For American Standard Toilet For Cadet 3. Replaces 738920-100-0070A, 3" Oversize. This flapper is made out of Hard Plastic, it has a silicone seal gasket, and a stainless steel chain. To install, turn water supply off. flush toilet to drain tank, and sponge dry. Next remove the worn flapper from lugs on overflow tube. Remove the chain from flush lever arm, and attach the new flapper to lugs on overflow tube. Fasten the chain onto the flush lever arm with hook. Adjust the chain to minimize slack when the flapper is in the closed position. Turn on the water supply and fill the tank.