Since the shelter used World's Best Cat Litter, that's what I stuck with. It costs more but it came in especially handy last year when I had to get JonJon's radioactive iodine treatment. The litter is flushable and safe for septic systems so I didn't have to store up a week's worth of irradiated litter pee hunks for weeks. I mostly throw it away now but it was good to have the alternative.