Love the concept of the product but the medium is too small.  I have a 9lb (short and stocky) kitty and she barely has enough room in the medium carrier.  Thank goodness she is short otherwise she'd be too tall for it and would have to be lying down in it; just not enough room in the medium and it does say for up to 15lbs.  The idea is great and it's easy to use but just not large enough.  Also if you put a small, thin towel in the bottom to go over the plastic, that falls when pulling the carrier and gets all messed up so I wish there was a cover to put over the plastic that would stay in place and be made to be taken out when you need to wash it.....