I have been wearing these Long Sleeve shirts for several years now. I wear them to work, and also outside of work casually. I like the Carbon Heather, and also the Heather Gray colors the most. The material on these shirts is extremely soft and comfortable. It is a lighter weight shirt than the k126 line of shirts. I find that the durability on these shirts are excellent. You will notice that the writing and logo on the sleeve will eventually wear off with general use and washing. However, the stitching in the shirt has never worn or come apart after over a year’s worth of daily use. These are great for warmer climates, and I often wear the gray color in the summer where it gets to 100+ degrees Fahrenheit to keep the sun off me. I also periodically will wear these in cold winters and layer them. I am 6 ft 4, with a lean build and blue baseball jersey I find the XL to fit well with plenty of room in the shoulders/arms/chest/midsection. The sleeve length is just right for my long arms. The Large Tall will also fit, but I find the arms to be a bit too small for my liking.
I love this line of shirts. The fit is great and it hangs nicely. The only down side of the heather gray shirt is that drops of water on it show up as almost black spots until they dry. This doesn’t happen with the black version. As I went to put it on for the first time, I saw some black spots and thought “crap, it’s got a stain on it and I’ll have to send it back.” I then realized that my hands still had a bit of water on them from my shower. Five or so minutes later, the spots were gone. It’s no big deal, but I have a feeling that being out in a light rain would cause a very strange look to the shirt.

The bottom line it that it is a great shirt, well made out of excellent materials. It’s just got this quirky thing going with water drops.