It's a US size S, but a Japanese size M. However, it's a bit slim. It's a very cool piece when worn fitted. I'm selling it because it's become too tight, unfortunately. It's perfect for slender people. Size: Length: 63.5cm Shoulder width: 34cm Width: 41cm Sleeve length: 12cm Adidas polo shirt with black and white stripe design. - Brand: Adidas - Color: Black/White - Size: UK 10 / USA 6 / EU 38 / JPN 9 / S/M - Design: Stripe - Style: Polo shirt Thank you for viewing.