I was using a clumping litter before the crystals. But when I got the Scoop Free litter box I used the crystals it suggested. I have not smelled the litter box at all. The cats seemed to be a little apprehensive at first so I left one box with crystals and one box with their old litter. Now I'm just using the crystals. For the box that isn't the scoop free box, the crystals are easy to scoop through to clean. I love the ease of use and lack of smell with this litter!!