"Keeps its shape" is not true - it loses its shape very quickly, and has to be reshaped by hand repeatedly. This is in contrast to other tunnels that have a spiral of wire, and keep their shape just fine. The cats have a marvellous time with it though.
I think this is a perfectly adequate tunnel and I bought it for my tunnel-loving cats thinking they'd appreciate an addition - but I was wrong. For some reason they just don't like this tunnel. The only thing I can think of that is radically different from their other tunnels is that this tunnel lets quite a bit of light in, whereas their other ones are very dark inside. I'm hoping they'll change their minds and decide to accept it because it rustles, rolls and rattles just like any good tunnel ought to. I'd happily give this 5 stars but the experts want to give it 1, so we've compromised at 3 stars :-)