GEL CRYSTALS with added freshener FAST ACTING ABSORPTION ELIMINATES ODOURS LASTS UP TO 4 WEEKS Prior to using any litter please ensure that the litter tray size is adequate for your cat. If you have a large cat then the average litter tray may be too small. This product is made from highly absorbent silica gel crystals. In order to get the best performance from the product we suggest the tray be filled to a depth of at least 5cm. All solids and urine clumps must be removed regularly each day. The litter may need to be topped up weekly to compensate for this removal. The urine is absorbed into the crystals and they will become clear when they have reached their absorbency capability. The urine will pool to the bottom of the tray once the crystals have been used to capacity. We also recommend the entire tray be changed, washed and filled with fresh litter at least once every four weeks. The crystals should last up to four weeks with one healthy cat if the litter is used correctly.