Purrrfect in more than one way!
Whether the tunnel is in it's compact or extended form, the shape, height, shape all combine to provide a sturdy structure that along with the material is attractive for the cats to scratch.  When extended the tunnel's material, open side hole & dangling pom poms make it an appealing play & stalk area. 
When not being used as a play area or soft & warm place to take a cat nap, this attractive structure nestles together into a compact & practical shape.