HealthSaver Bedwetting sheet size 42cm x 54cm for use with the Healthsaver Bedwetting Alarm BWA PA 40 33. Place the bedwetting sheet on top of the bed mattress and underneath the bed sheets. Place the BWA PA 40 3 alarm monitor (supplied seperately) as far away from the bed as possible, as it is fairly loud and designed to awaken even deep sleepers. Our bedwetting sheets are easy to wipe clean, are waterproof and re-useable.