A diaper cover provides the waterproof layer needed to keep your child's clothing dry when using cloth diapers. A Diaper cover should be used with flats, cloth nappies, fitted diapers or prefolds. While using a diaper cover, you can just replace the inserts/prefolds every 2-3 hours, and re-use the diaper cover after wiping. If pooped, you will need to replace the diaper cover. On an average, you will need 2-3 diaper covers per day.