Fitted nappies, prefolds and traditional flat cloth nappies all require waterproof covers or wraps to prevent otherwise inevitable leaks. Choosing a good cover is essential to getting the most out of your nappies. So gone are the days of crunchy, airtight PVC cover that leaked more often than they didn't, today's modern fabrics will keep baby dry and comfortable while allowing delicate skin to breathe. If you are using fitted nappies or prefolds expect to need 1-2 covers for every 4 nappies, if you are using traditional flat cloth nappies the ratio of covers to nappies will be a little higher.