Pocket Nappies have a waterproof cover and a pocket opening - an absorbent insert is popped into the cover. This makes them fast drying as the two parts separate and unfold before washing. This also makes pocket nappies easy to boost (add extra absorbent inserts) for nights and heavy wetters. Boosters are sold separately. Many pocket nappies are One Size Fits All and adjustable by snap closures on the front of the nappy. This makes them a very economical option. Sized pocket nappies are available and give you a perfect fit from birth to potty.