This product is great in concept but fails on delivery. I liked the idea of not having to scoop the waste but...it still left a stink even though it pushes the waste into the waste reserve area. I also found crystals and dust from the crystals at the box and throughout my house which to me is more of the problem.  The sides of the box should be higher to avoid crystals from escaping the box when cats dig.  Also, the tray should be plastic (cleanable) with crystals in it with a disposable cardboard waste reserve area so you only have to buy replacement crystals and not the tray again.  It seems wasteful and the trays are too expensive to keep buying.