Are they universal? Can I use a Toto fill valve on a different brand of toilet?

There are universal kits at the hardware store. Couple of different designs.

Most (but not all) toilets use interchangeable/universal parts for the internal workings.

Thanks. I'm asking because I have a toto spare on-hand but need to R&R a valve on a non-toto toilet.

I shopped online and toto valves are indicated for toto toilets. And then there are valves that are universal but not sure toto is included; there are aftermarket valves that specify use for toto.

So it seems that toto may be different from other common brands but not sure. Not sure what would be different, if anything - diameter of the fill valve at the bulkhead? The shape of the bulkhead hole?

I replaced the two high use toilets in my house as they were constantly needing plunged or snaked, but left the other 2 rarely used builders grade toilets. I installed American Standard Champion 4 (i.e. the one they used to advertise flushing 18 golf balls) after a friend's recommendation.

I can use any Fluidmaster or American Standard fill valve.

However, I have to keep two different flush valves on hand. The builders grade toilets use universal flush valves purchased at any hardware store or big box store. The American Standard uses an enormous 4" flush assembly which is why it works so well.

They're very inexpensive. I'd just buy a new one.

Fill valves are universal. It’s the flappers that are often different. The differences you see are probably just different types, but they’re not proprietary. For example, Korky makes valves that have an external float, internal, and also a pressure type somehow. They may even make a ballcock valve still, but I don’t know why anybody would use one.

That’s a lot to say that the fill opening size is identical on every toilet I have ever seen, even on eighty year old ones I’ve had in old houses.

Just buy a new Fluidmaster. They're usually around $15 and should take no more than about 10 min to install.

Generally just use the Toto. The other toilets are mostly for guests.

I already have a spare Toto valve. And if possible, I'd prefer to just keep 1 spare Toto, rather than 2 spares - 1 for the Toto, 1 for the other toilets.

Sounds like the fill valves are universal. I'll use the Toto spare I have an then just buy another spare.

Thanks!