All-in-Ones. An AIO diaper consists of only one piece. The absorbent material (insert) is attached to the outer shell. AIOs are the only diapers that don’t require “stuffing” and are super easy to use. Some AIO diapers take slightly longer to dry. These diapers are considered the easiest style to use and are very popular for dads, day care, and anyone hesitant to try cloth diapers