I'm 5'9", 85kg, 41" chest, 34" waist, 15 1/4" arms, and I bought a size Large shirt. This shirt, after washing and drying, hugs the arms and chest and is overall a more slimmer fit than expected like previous SBD shirts. The ends of the sleeves on my shirt hit right at mid-bicep. Armholes are a bit tight. The length of the shirt is just okay, although I would say that due to my butt and hips the shirt doesn't stay down during the lifts so I have to pull it down every now and then, otherwise the material bunches up at the chest area and sits at the top of my butt instead of covering my butt.
For competitions or for showing off your guns or whatever personal preference, it's a really nice shirt, but if I could go back in time I might have bought the size XL and tailored the sleeves if I had to. Personally, I like slim fitting shirts, but this one's just a tiny bit too slim which is not what I expect when I order SBD shirts. Size L in this new shirt almost fits like a relaxed fit American size M. If you have the shirt that was previously released, the black SBD apparel shirt, which I do, the fit is similar to that, but this new blue one is just a little bit more slim-fitting all around. For this new blue shirt, I would say it's slightly tighter than the size L compared with the other SBD shirts.
Overall quality is great, and SBD lives up to it's name, as usual. Customer service from Inner Strength is always awesome, too!