I’m a bit confused regarding toilet seat size. In both my parents’ houses (mine and in laws), they both have 2 different sized toilet seats. The one that came with the developer being small size and the ones that they upgraded are obviously bigger.

But the handful of shops that I’ve been to said that there’s no such thing, all toilet seats are same size. It’s just the shape that’s different either round or oval. And the other difference is the distance from the wall to the hole.

Very confusing. I’m 100% certain that there are different size toilet seats.