Super!
Really robust and resilient, our 5.5 kg cat jumped in all possible ways in/on/through/out the cube and it is still ok after more than a year. The tunnel is nice, but the cube is absolutely loved! And to play with a toy while he is in the cube is pure joy! For the reference: he is a very beautiful, quite grumpy 7 years young cat.
Both cats like the tunnel, and they love playing with it when it is connected to the cube.
A big plus is that we can easy take it with us when travelling with the cats.