Crystal Litter is a relatively new product whose primary benefit is SUPER ODOR CONTROL. It is made from silica sand (SiO²). Through processing, this sand is converted into crystals that contain millions of microscopic pores which exhale moisture from cat urine. This process also kills bacteria. The crystals also pull moisture from the droppings, which further minimizes odor. THIS ADVANCED TECHNOLOGY PROVIDES THE GREATEST ODOR CONTROL OF ANY LITTER. Crystal litter is rapidly becoming the favorite among those with smaller living quarters, such as townhomes and apartments, because of its very superior odor control. CHUNK VS ROUND: Chunk has an irregular shape and does not roll far if displaced from the catbox by a playful cat. ROUND lasts a little longer and is ideally suited for automatic litterboxes and tray refills. ROUND CRYSTALS ROLL FAR IF DISPLACED FROM THE LITTERBOX; A LITTER MAT IS STRONGLY RECOMMENDED!