Awful chemical stench
The tunnel itself is of nice quality, and the outer material feels "natural" but the inner material stinks of chemicals (similar to worst quality plastic) so strongly that we had to remove them (bought 2) from the house. Several cycles of machine-wash and airing outside for 2 weeks didn't help. The cats seemed to be bothered by the stench as well as they didn't use these tunnels, unlike another one.