I have this one. Charlie is a large syrian and it's a good size for him. I like the corner shaped ones as Syrians tend to choose a pee corner - usually a corner of the cage, and this fits in a corner - Charlie pees in the back corner of it, and keeps the front part clean so he can sit and wash in it
So he stands with his butt facing the back corner (hence it's raised at the back).
Amazon.com : Trixie Hamster Potty Corner Litter Tray For Mice Hamster Gerbil Cage House. Size: 16 × 7 × 12/12 Cm : Birdcage Litter : Pet Supplies