Blue Naturally Fresh Multi-Cat Clumping Cat LitterBlue Naturally Fresh Multi-Cat Clumping Cat Litter is a major advance in cat litter. A proprietary blend of the fibrous materials found only in walnut shells is proven to neutralize odor better than any other multi-cat litter. Our super-absorbent formula produces hard clumps within 15 minutes, which makes clean up simple and mess free. At least two times the odor control of other leading multi-cat litters. Unlike clay litter, which often throws off silica dust, Blue Naturally Fresh is virtually dust free so you and your cat can breathe easier. Blue Naturally Fresh does not stick to your cat's paws so it's less likely to be tracking throughout the house.