This is a special order short-sleeved shirt from STUDIOUS. Size 38 (equivalent to L due to its relaxed fit) Made of nylon, it's a tech material with a crisp feel. I've worn it about 10 times, but the material is durable, so I don't feel any deterioration. It sold out quickly after its release, so you probably won't see anyone else wearing it. Feel free to ask if you have any questions.