I purchased this but it's unused. I'm selling it because I no longer have the opportunity to use it. The following is quoted from the HP: Purchase price: 8,000 yen This product helps you quickly develop the habit of sleeping on your side to prevent the tongue, soft palate, and loose throat tissue from falling back and blocking the airway. It helps reduce snoring caused by throat problems. It's large enough to prevent you from sleeping on your back at night, so you won't end up sleeping on your back or hurting your spine like you would if you wore a small or hard supporter. You can adjust the air capacity of the airbag to find the most suitable sleeping position. If you wish to exchange the airbag for free within the 3-month warranty period, please send a message. This backpack features a 3-point fixation on the shoulders and waist, so it won't shift or slip over time. Please note that we will randomly ship two versions: a buckle strap and a touch fastener strap. Size Guide - There are two sizes. Measure the width of your back between your armpits, but do not include your arms. The large size is for people with a back width of 16 inches (40cm) or more. People of medium build are recommended to choose the large size backpack.