It's close and many people have 5/8ths, it's just some keets are smaller than others and there have been report of keets getting stuck or getting out with 5/8ths, and not with 1/2 inch, so most people just feel 5/8ths is a tiny bit too big. There is no way a keet could get stuck in 1/2, but as I was saying earlier most cages have a bit bigger openings in certain places like on the sides, so the 1/2 inch cages just barely have small enough to keep them from getting out in thsoe side bars, and the 5/8ths have even bigger openings on those sides which end up being big enough for them to get stuck in. Most keet can't get out of 5/8ths but if there is any bigger openings in the cage you will have problems, its just best to stick with 1/2. Anyways best of luck and best wishes everyone. Jloc