Microfleece Stay Dry Sleeve is specially designed to be used with any One Size Cover. Just stuff the sleeve with inserts, tri-folded prefold or flat and place it in the diaper cover. Sleeve will keep all inserts in place, preventing them from shifting around and bunching up. It wicks moisture away from the skin and provides stay dry feel. There are occasions when you might need to use diaper rush ointments that are not cloth diaper safe. The sleeve is a great way to protect your inserts.