I think the compartment boxes have a small Area Like a small room when they first go into the nest box, then they'd have to climb down into the actual nest box - I think they're made for birds who startle easy so they don't jump in/out and break eggs, kill babies
I would think since they have a long tail though it would need to be fairly wide.
the one we just made for our Conures is 8x8 Square and their tail fits in perfect, I just don't see a IRN'S tail fitting a 8 wide box.