They are exit seats only if on a 757 !. They are right at the exit that will probably be in use though so you will get bashed and bumped as the pax come on. Wait till near the end, and the overhead locker space will only be behind you. Watch its not too cold and drafty. The seals on those 757s can occasionally be a bit drafty ! 12 A is NOT a premium seat albeit 12B is !