This litter box is the best.  I just bought my second (the large version) after haveing the regular size for about 3 years.  The box is great, you just fill with litter to the line.  When cleaning, roll the box over and the clumps fall into a sliding tray and the other litter is sifted through a grate.  There are clasps that hold the lid on tight to the bottom.

 The regular size is fine but keep in mind the grate takes up about 1/3 of the box.  I have 2 cats and they don't seem to mind.  I just bought the larger box since they are getting bigger. 

I would recommend this box to anyone. ...