Baby Diaper covers are meant to cover your baby's diaper to prevent his/her clothes from getting wet. Like baby diapers, baby diaper covers come in many forms. They may be contoured and can fasten with snaps or Velcro. Some baby diaper covers resemble underwear. Baby diaper covers are either made from polyester or vinyl to prevent wetness from getting on baby's clothes. These are ideal for covering baby's diaper during the day. Some babies have sensitive skin. For these babies, try diaper covers that are wool or polar fleece. These also may be contoured with shape with snap and Velcro fasteners. Others come in "Boxer-like" shape. Some prefer theses for nighttime use because they allow air to circulate.