For bedwetting対策 (measures). It's like a wrap skirt, and the waist is made of elastic fabric. It doesn't seem to be completely waterproof, but it's water-resistant. It's supposed to prevent leaks even to the sheets. My child didn't wet the bed while using this, so it's in a clean condition. Peace of mind when traveling. Can also be used as a futon (because there are snaps at the hem, it won't come undone).