I bought this for use with a PetSafe Scoop Free litter box. I have a reuseable tray and have been experimenting with various types and brands of silica litter to see what would work the best. It turned out that no other brand could compare to this one for how it works with the rake, how low odor it is, and how long it lasts between changes. I have three indoor cats, so I knew each bag would not last two months. I anticipated it lasting about 2 weeks, but have been pleasantly surprised. I've cleaned and refilled the reuseable tray three times now, and still have yet to empty the first bag. Each time I change it it's lasting 8 to 9 days before the crystals are saturated. After about 4 days I do lift the litter box and remove the scat that's been raked, since with 3 cats that does fill up faster, but that's easy to do and it doesn't smell.