These refill trays make it super easy to change the cat box. The whole box flips up to slide out the old tray and slide in the new. 

The tray takes about two minutes to fill and set up. When it needs changing the box has a lid to slip on and throw the whole thing away. 

Over all super quick and easy to use. No need to scoop, just slide in. Works perfect with the box, no issues with it fitting or anything. It does take some extra space to store refills if you need them often, so make some closet room.