Finally a technical baselayer that fits. I use these under my BJJ gi pants as a rash guard. It took me forever to find something that fit me. I ordered others that were supposedly 4x, but they were more like 2x in size. The Nike baselayers fit true to size and are standard American sizing. Remember these are light compression garments so they are meant to fit snugly. You should feel a light squeezing sensation. They aren't as robustly built as some purpose built rash guards, but they work for me since I wear them under my gi pants. I've never liked fight shorts. Not a good look on a guy my size. Lol Oh one last thing make sure you're wearing boxer briefs under these. Regular boxers are a no go and bunch up.It fits true to size, for a big guy my size..Nice fabric. Comfortable fit. Sits quite low on the waist. Not much compression.Son likes themLikeGreat fit, warm enough for a cool gym, cool enough to workout in!Best most comfortable fit.Fits well and very comfortableVery good looking, well fitting smart shoes, brilliant for a Smart-Casual occasion or workplace. I definately recommend this for both comfort and appearance