Will an A2 aperature fit an A1 upper? I'd like a ghost ring option in place of the 375m zeroed "L" marked aperature on the A1 sight. Don't want to drill out my A1 sight since there's no park tank handy here. Would like to just be able to swap out one for the other.

I've not looked around real hard yet, but some ads I've seen sell the A2 sight as an assembly only, I just want the aperature.