Ms B Maki
I bought this litter box for wood-pellet-type litter, and it works fine. When cats' wee touches the pellets, they disintegrate into sawdust, which falls through the sifter, leaving the unused whole pellets above plus any solids (poos) which can be easily scooped out.
This is a good product but not for a household that has more than 1/2 cats. I currently have 4 cats and have found that the clumping litter - after a 24-48 hour period - goes into a solid mass which cannot be sifted. I ended up putting the entire contents of the litter tray in to a black bin bag. Again, this is a good product but not for a multi-cat household. My cats now use three Giant Van Ness sifting cat litter trays.