Lisa - The sifting liners won't work with ferrets. The premise of how these liners work is that they are used with clumping kitty litter, and when sifted, the clumps that are formed aren't small enough to get through the holes in the liner, whereas the rest of the litter is. There are two reasons you can't use them: 1. You can't use clumping kitty litter with ferrets. About the only kind that's good for them is pelleted, low-dust litters. The reasoning for this is twofold; the dust that is made by these litters is harmful to ferrets' respiratory systems, and the tiny pieces of litter can easily become impacted in ferrets noses, requiring trips to the vets, and hefty vet bills. 2. Even if the litter worked, you wouldn't want to put a soft plastic like this in a ferret's cage. They could ingest a small piece of it and it cause a life-threatening intestinal blockage. If you have been using regular kitty litter, I recommend any of the following as litters: "Yesterday's News" brand pelleted cat/small animal litter, wood stove pellets (you can get from any tractor/farm supply store), "Woody Pet" brand pelleted litter (also from tractor supply stores, and pet stores), and rabbit food pellets. I've used all but the rabbit food, and can say that they work very well. ~Keri [Posted in FML issue 4449]