Love these! Except they can be really pricey to buy refills. I have heard that you can buy a more permanent tray and refill them with crystal litter. I’ve also heard you can just top up with crystal litter to extend the life of these trays. They LDR about two weeks if you have two cats who have normal bathroom habits. I have one cat who drinks half a gallon a day and pees like a race horse. So I go through these more often than I’d hoped. But overall recommend as they make your life more convenient and the smell is so much better than traditional litter boxes.