I have three cats, small (6lb), medium (8lb)  and large (19lb). All are normal size and weight for their breed. It appears that they have picked out which level is thiers and they enjoy playing with each other on it. A word of caution. If you have more than one cat be prepared to have have to work around them when assembling or, if you don't want a feline supervisor and inspector, lock them in another room till your finished.