bunkajin 3 I generally wear a U.S. size L. For Japanese goods (such as Uniqlo and Muji): XLThe ad for the item says, "Fit: True to size. Order usual size." According to the sizing chart for this shirt, I am L on some criteria and XL on others. So, I went with XL. When it arrived, I found it to be rather tight across the chest and back. Also, the sleeves are cut quite narrow, so that the fabric hugs my arms. It certainly is wearable, but not slightly loose, as I had expected from XL.So, I ordered one more, this time in 2XL. It's better, but even that one is snug across the shoulders. Look at the model in the ad. If your physique is even somewhat more muscular than his, you may have the same reaction to the fit that I did.Despite this, if the UPF 50+ 99% UV Protection claim is true, I'm happy to have them. The price is reasonable; just be careful about the size you order.