It's a US size 11. I bought it on Amazon, but the size didn't fit, so I'm selling it because I repurchased a different size. ¥8,800. I wore it once, paired it with my smartphone, and then deleted the pairing. You can find more detailed information on the Amazon website. -------------------------------- AI Information Below: b.ring smart ring with IP68 waterproof rating, featuring health and sleep management functions. - Brand: b.ring - Model Name: b.ring Smart Ring - Functions: Health management, sleep management, pedometer - Waterproof Performance: IP68 - Compatible OS: Android, iPhone - Size: Japanese size 23-25 / Inner diameter 64.5mm Thank you for looking.