if your cats like the Sportpet play cube, they'll probably like the Mystery Triangle. the Mystery triangle is diamond / octahedron-shaped with holes in 2 sides. in one side is a large metal grommet which allows a rope to run through with a toy on the end. the idea is that you can pull on the other end and play with the cat while they are inside. my little guys had the toy detatched pretty quickly, and if any of your cats like chewing on stuff, they probably will too. most of the toy is made of a parachute-type fabric with springy wire to give it structire, but a couple of the sides are made of mesh fabric. on the one hand, the mesh allows pets to see through the triangle, which can be fun for multiple pets playing together. on the other hand, it tears up a bit faster than the parachute fabric. the triangle will sometimes collapse during play, but this is no danger to pets and really is a good thing...some of the newer Sportpet Play Cubes get bent out of shape rather than simply collapsing. it's much easier to pop the toy back open than to reshape the wire, so...yay collapsing triangle!!

also, if you're like me and you have an obsessive compulsive streak, there's no real "top" or "bottom" to this toy. with the play cubes, when the cats aren't using them, i'm constantly flipping them "right side up" so that the streamers are hanging from the top like they "should be". i don't have this problem with the Mystery Triangle.

Pros: collapsable for storage, no such thing as "up"

Cons: could be a little sturdier

I did not think my cats would use it alot, They have barely come out of it and we have only had it for 2 days. Very reasonable at $4.50 at wal mart . Very cool toy . I like that they can play with it alone or you can pull and wiggle the hang toy with it to make it more interactive.

A similar cat playhouse can be found on pet360.com here: http://www.pet360.com/product/16439/smartcat-bootsies-bunk-bed-cat-playroom

Pros: Easy to use " pop up assembly and folding storage

Cons: none yet

My four cats love this! They roll around and play in it, they hide and attack from it, and they sleep in it. Yes, sometimes it does collapse down, but not all the time, and worth the trouble. It takes about 2 seconds to pop it back open.

Pros: None

Cons: Everything

I originally got this for our kittens because they love the kitty tunnel we have but it turns out that all the cats love it-the playful ones anyway!
In addition to the holes that they can play in and out of, there is a toy hanging in the middle so that the cat in the triangle can amuse themself!

Pros: Keeps them occupied alone for a while

Cons: Sometimes collapses in on itself