This indeed is the replacement part for the flapperless toilet which Home Depot used to sell. I recommend it if you need one :)
I absolutely love the flapperless toilets and wish that they would again be for sale. We purchased two, in the taller "handicapped" size because we are taller people, and really like the way they work. Gone are the chains which tangle, the paper clip to adjust chain length, and the falling off, the flapper not sealing --- you know these things, if you've used toilets for any number of years, lol :)
It would be nice if this part were "cleanable" as the reason we needed to replace the original had to do with a bit of granite-silt coming through our water pipes and clogging this piece. There's a filter, but no way to dis-assemble and truly clean if something gets in.
Anyway, glad the replacement is available. Got about 10 years out of the original part and hope to get another 10 years use before needing to replace.