The PETKIT waste bags are specially designed for use with the PETKIT litter boxes Pura X and Pura Max. Each roll contains 20 individual bags. Made from high-density polyethylene (HDPE), the bags are biodegradable, making them perfect for the environment. It is recommended to change the waste bags every 3-4 days. One roll lasts for about 2 months for 1-2 cats.