Simple Solution Cat Litter Odour Eliminator keeps the litter tray smelling fresh and clean. Each 500ml trigger spray bottle contains over 40 litter tray treatments per bottle. The Pro-Bacteria (TM) formula is activated when your cat uses the litter box. The Natural beneficial bacteria and enzyme formula is activated when your cat uses tray. Shake well before use and apply spray 10 - 15 times over the litter. Stir the litter lightly, then respray. Reapply as needed, and change the litter when necessary.