If you have certain Kohler toilets, you have to use this odd proprietary type of flush valve as a replacement. They're made in two heights, so if you have a low-tank toilet, you need the shorter one. If you have the standard-height tank, you need the taller one that has the longer tube extending a few more inches below the flap-valve area. They look exactly the same otherwise, so make sure you get the right one. Either way, be careful while you install it, and use the new gasket that comes with it. The three bottom tabs that lock it to the tank are easy to break off if you don't do things right. I actually broke the one I already had while trying to replace just the gasket and had to buy the whole new valve. Here's what I did: Unhook the tube and chain going to the old valve. Rotate it about 60 degrees (direction doesn't matter) until you feel it release when its tabs line up with the "points" of the triangular opening it fits into. You may have to use downward pressure to get it to move. Use a file or heavy sandpaper with a backing stick to file to a little bit of a slope on the TOP edges of the three tabs on the new valve. This will help to keep it from binding on the under surface of the tank as you twist it into position when installing. Remove the new gasket and flap and liberally grease the tabs, the top and bottom gasket seating area, and the new gasket itself. Don't use petroleum jelly, it can affect some types of synthetic materials, so may not be good for the gasket. Plumber's grease is good, but other slick, but not too thick lubes will work. I used reloading case lube mixed and a water-soluble gel, but even some skin lotions, soap, or dish detergent combos would likely do. Clean the tank bottom where it will sit on the top and underside, and lube it, too. Pencil mark the tank about where the points of the opening are, and far enough out so you can see the marks with the valve in place. Mark the top of the valve gasket flange at the tab locations with something like a silver sharpie, so you can keep track of where the tabs are when you're rotating the valve into place. Determine which tab you will need to insert at which point in the tank bottom to get the flap where you want it after it's turned 60 degrees. Put the gasket back on the valve, and FIRMLY push straight down and rotate it about 60 degrees in the correct direction. Doesn't have to be exact, just use the markings to see that the marks on the valve flange end up about halfway between the markings you made on the tank. It can take some force to compress the gasket (that's why it helps to have the flap removed), so be sure it's compressed enough to turn without stressing the tabs, or you're likely to break off one or more and have to start with a new valve again. Don't wobble it as you work it into place. Reinstall the flap, fill tube, and pull chain.
