I have two 2yo cats, one is 7 lbs and the other is 12lbs.
The tunnel was too small for our larger boy; he could get through it just fine if there was a toy on the other end, but he didn't hang out in it like he has wider tunnels.
He loves the basket configuration, though. it's his favorite hunting blind, for both hunting toys and his bother. Would definitely buy a second if if came in a wider size (same length, and maybe 1.5x the width? 12"-13" seems to be the ideal tunnel diameter for both cats).
The material and different sized holes are great for hunting through, and I definitely recommend the product as-is for smaller cats.