These trays are amazing.  We have one tabby male cat and we only have to change the tray ever 20-25 days.  There is very little odor (only when the cat first uses it before the box scoops the mess), and the litter is a great indicator as to when you need to change the pan.  I don't even have to scoop the tray in between trays most of the time.  Glad I got these in exchange for my honest opinion!