Many pet cemeteries across the nation require the use of a pet vault to improve the aesthetics of the cemetery from ground settlement.They also protect the cremains or body from rapid deterioration and moisture in the soil. They protect the contents from the weight of the heavy ground. They aid in possible environmental issues. They are made from the polypropylene family, and are light weight and inexpensive. Some people prefer to use them when they bury a pet in the back yard as well for all of the above reasons. Often vaults for children can cross over for pets.