Wool is the most natural, and devine nappy cover type. It can be temperature regulating, and is great to use day and night, winter and summer. Unlike PUL which you have to was after several nappy changes, as long as you dry your wool cover well in between uses, you can re use your wool cover for many, many more nappy changes. That means less work, less washing. You will however need to replace the lanolin when you wash your wool cover, this is an easy job to do though.