I have had these for years to be honest - But in terms of size that I have, I know I have the largest they make, and these are two sizes below that - so they are Large if I recall correctly. But, it's easily expandable.
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Nope, I removed the perches, and used a pencil to do my marks. Then drill pilot holes to make my life easier. From there its just screw the mounts, and the hide literally slides right in. Very VERY easy access.