Catsan Smart Pack is the first inlay pack for the cat litter tray consisting of an absorb-active micro-fleece and hygiene layer. The micro fleece actively absorbs the liquid underneath the Hygiene Litter and locks it in safely. This improves the odour binding and the litter stays noticably drier and fresher for longer. Just the way we like it. Each unit last approx 15 days making a total of one months supply per pack.