As it stands right now, Apple's only iMac option comes in with a 24-inch display. The company quietly removed the 27-inch option some time ago. And while there have been rumors that a replacement is on the way, we're still waiting for that to actually happen. And it sounds like Apple is at least toying with the idea, anyway.
Apple reportedly prototyped three different 27-inch iMac models in 2021, including one with an M1 Max chip