No matter how often you scoop out the clumps, you may miss some smaller pieces which gradually build up and begin to smell. With ARM & HAMMER® Odour Alert® clumps turn blue when wet for easy removal. It’s the only litter with crystals that change colour on contact with urine. Now even the small pieces that cause odours can’t hide. Provides rock-solid clumping for easy removal; 99% dust free and low-tracking. Easy-pour, no spill spout.