I normally wear a Large, but I ordered a Medium after reading many reviews suggesting that the fit was a little loose. The Medium fits perfectly without being snug around the waist.

Height = 6ft
Weight = 217 pounds
Chest = 43”
Biceps = 16”
Waist (around the love handles) = 39”

I've included a drawing with measurements for the MEDIUM size Opna shirt that I purchased (see image)

I tried several inexpensive brands of long sleeve moisture wicking/performance shirts to find one I could comfortably sleep in (slippery material, close fitting so it doesn't tangle, but not compression/second skin because at my current weight I'd look silly). This brand is higher quality, slightly thicker, more opaque, fits perfectly, and looks the best, too. Wide shoulders that keep a little shape even on my quite wide shoulders (I lift a bit), body just skims my excess fat without hugging it, so I look as wide shouldered and slim waisted as I currently can. So good I can wear them as casual wear. I bought XL and I'm borderline XL to XXL in most name brands.

I ordered 4 different colors and I was surprised to find that (according to the labels) the 4 shirts were made in 4 different countries (China, Haiti, Tanzania and Madagascar). I am 5'10" and weigh 163 ;bs, but my past experience with athletic wear from China ( I thought they would all come from there) made me cautiously order the next size up so I ordered Large. I have tried on all 4 shirts and so far I have not noticed any differences in stitching or fit. The fit through the chest and length of the tail is good. The arms run a bit longer than I would like. If I were ordering today I would order medium. I ordered the 4 shirts for a November European trip so I won't be abale to update anything here until after I have worn them (and washed them) on my trip. I will post an update on my experiences with these shorts if there is anything negative after wearing and washing. No post updates mean the shirts performed as expected.

I use this shirt mostly for bicycle/transit commuting year-round in the Denver area. I find this shirt can be warmer than cotton since it does a better job of keeping the skin dry when you sweat. If I work up a sweat riding to the transit station - I found waiting around outside in a damp cotton shirt can really chill the body. I used this shirt this last spring and some morning rides were cold rain or slush-snow rides with temperatures around freezing. I was comfortable in the shirt wore wore under a light rain coat. Too early to say anything about durability. But this shirt meets the need of an under-layer when exercising in mild colder weather. I would like to see this same material offered in a full T-neck collar for below freezing temperatures.

5'6" 140lbs. I ordered a size down as i figured I should after reading reviews.
the shirt is still a little loose even though i got a small when i should fit (barely in the range) for a medium.
It was still a welcome mid-summer purchase for the cost, considering all the local stores and name brands have their prices jacked upwards of $30 per shirt.

+ Sleeve length. In spite of the shirt being a little loose with 1 size down, it still fits well all the way down to my wrists and doesn't ride up my forearms when testing for range of motion. I have slender/normal shoulder width but long arms (70.5" armspan).
+/- 100% polyester. you may or may not like it. it works well enough, though most of the athletic shirts I have are 90/10 (polyester/spandex). the 90/10 seem to stay more snug on me.

While it doesn't quite have the feel and comfort i'm used to, it still works, and has served as a great backup to my brand-name shirts.

Love the richness of all the colors I ordered and feel of material...

Unfortunately size I ordered was extremely too large...

I'm return all of them and will order just one color in 2XL & XL...

Once I determine what is correct size I'll order all the same colors ordered originally...

The colors are bright & brilliant...
The material silky smooth...
Looks great...

Unfortunately 3XL was way too large for me...

I ordered XL & 2XL to see which fits...

I just got the XL & 2XL. I tried on 2XL and it fits...

I tried 2XL in gym, exercising, walking around and it holds up after washing...

Only issue is sleeves & tail could / should be longer...

I actually prefer Vapor Apparel fit & style... The sleeves are longer and never pull up my arm no matter how I move or flex my arms. The tail of the shirt is longer and goes just below my crotch which allows me to wear compression leggings with tee & private parts are covered. I don't wear gym shorts over my compression leggings so I need tail of tee to be long...

Wish Vapor Apparel had more colors...

Since Vapor Apparel does not have as many colors I found these and other than length of sleeves & tail they're good quality for most part...

Vapor Apparel are better but don't have color selections

For work I wear either a dickies brand button up work shirt or polo shirt - both solid black. These shirts are perfect for those colder days when I would like to have a long sleeve shirt - I just wear this shirt under my regular uniform shirt and most people think I have a long sleeve shirt on. It's just enough to keep me a little warmer on those days it's not quite cold enough to put on a jacket. Another use I've found is that they're great in the pool if you don't want to get too much sun on your body. I'll probably buy more in the future. Only complaint is that the seams appear to be cheaply made, and hopefully this will not cause a problem in the future. I bought 3 of these shirts, and each has been through the wash 5-6 times and so far no problems.