Each nappy has a certain capacity for the amount of liquids that it will soak up. When you want your nappy to go that bit further (such as when your baby is going through a period of heavier wetting, or if you are wanting the nappy to last through the night), simply add a booster. A booster is usually a rectangle piece of fabric, made of absorbent materials such as cotton, hemp or bamboo. Inserts can also be used inside Pocket Nappies as the absorbent part of the nappy.