We know that piggies most love things they can crawl through or crawl under, so we're always on the prowl for something new to entertain them.
A few months ago, I happened upon Super Pet's new Natural Corn Husk Tube in an independent pet supply store. My girls enjoy their Chubes and Chewbulars well enough, but I could tell some of the zsa zsa zsu was gone. So I bought a large one, popped it into the cage, and waited to see the reaction.
They became obsessed with the thing. Such shredding and tearing I've never heard, and when they needed a break from tearing off the corn husk they worked on deconstructing the tunnel itself. It took them just about 3 days to strip the thing bare, and the edges of the tunnel were so raggedy it looked like badly made fringe. I almost felt sorry for the thing under their relentless remodeling.
The Corn Husk Tube seemed to provide a more-than-adequate challenge. Where the veggie-dyed paper on the other tubes I mentioned comes off fairly easily, it takes serious effort to strip a Corn Husk Tube down to the cardboard. The bonus is that the corn husk has a delightfully noisy crunch that clearly appealed to the girls' taste buds. There was a clear sense of accomplishment in that 2x5 C&C cage when the tunnel was demolished.
Unfortunately, when I went back to the store they didn't have any more -- and continued not to have them for weeks. Searches in other stores turned up nothing. In the meantime, the girls made it clear that everything else I offered them fell far short on the satisfaction scale. (I felt like a negligent pet parent. [slapping my hand punitively] Bad mommy! Bad BAD mommy!!) Thankfully, I finally found the tubes on Amazon and ordered several.
Young guinea pigs definitely need the medium size, and full-grown pigs definitely require the large size. (The medium size will be outgrown quickly enough.) I'm starting to see them more consistently in brick-and-mortar stores (particularly independent retailers), but online retailers still seem to be the most reliable sources.
When you do find 'em, do yourself and your piggies a favor -- buy two (or three).