Toto uses two different flush valves...one is by Korky (made for Toto) and I'm not sure of the other. Both work well. The korky version has one wear part that is available at Lowes and any plumbing store. The flappers are avaiable at Lowes as well. Prices, about $3 and $10 respectively. There is another company that makes a soft-close seat. It's good when there are children around and is nice for adults as well...no late night bangs or caught fingers or other parts. There are generally two sizes of toilet seats: round, and elongated. Most will fit. the differences are exact fit and color match. that is subjective, but they will fit. I like the soft-close feature.