ROUND is specially designed for use in automatic (electric) litterboxes, such as Scoopfree® and littermaid®. Many users with standard litterboxes also prefer round because it has a slightly longer useful life, and is more gentle on the cat’s paws. The only drawback is that the crystals roll far on hard surfaces if displaced by a playful cat.
CHUNK style is generally preferred for standard litterboxes. The irregular (chunk) shape crystals will not roll far from the box if displaced by a playful cat. They track less than other litters because of their larger size.