I got the scoop free premium blue Crystal's for my scoop free litter box and it works great! My cat took right to it and started using it. I have always used a pebble litter so this was an easy transition for my cat. I love the fact that there is no odor. I've been using it several weeks now and I can't smell anything coming from the litter box. Its recommended that you chande it every 3 weeks for one cat and it has a place to write on there when you changed it, so you can check if you forget. I love it!