Instructions: Fill your clean litter box with at least 1.5 inches of Fresh Step Crystals litter. For best results, do not add any other litter products or additives to the box. Regularly remove solid waste, and dispose in trash. Do not flush. Once every 20 to 30 days, empty entire litter box. Dispose of used litter in trash. For more than one cat, shorten the usage cycle. Recommended litter replacement for 2 cats every 10 to 15 days, 3 cats every 7 to 10 days.