Purchased new in May 2025. I've been using this since the S size, and I sized up, but I started sleeping on my stomach and only used it a few times before storing it. Perhaps because I've been using this pillow since my newborn days, people around me often comment on how nicely shaped my head is. The following is quoted from the HP. Please purchase only if you don't mind it being used. I discarded the box, so I will pack it to maintain its shape as much as possible for shipping. GIO Pillow, a flat-head prevention pillow usable from newborns ■ Product Contents 1 pillow body + 1 cover ■ Body Size M size Approx. 230 x 330 x 60mm (4-24 months) Suitable size: Head circumference 41cm or more Scientifically developed 3D structure to prevent flat head. Excellent breathability with air mesh to prevent heat rash and stuffiness. Thorough hygiene management using advanced UV sterilization machines and advanced packaging machines. The only baby pillow recommended by the Korean Atopy Association. KC Safety Certification obtained from the Korea Apparel Testing & Research Institute (KATRI), a government-approved certification testing institution. KC certification obtained for both the pillow cover and the pillow itself.