My two wild children kitties love this cat tree.  Not so hard to put together!  They climb, run and leap at fast paces, hang upside down..and I'm shocked that the hanging toy has been on for a few months now!!!!  The older cat likes the car condo in the bottom.  The greens are not necessary.   Would recommend to anyone with rambunctious cats.  DOes "shiver" a little when they come at it full blast but not even close to tipping over!!!!!!