I am 6'3 and of athletic built. I usually wear L, but just to be on the sure side I ordered XL with this. It arrived within two days, the material is super nice, very soft and gentle on the skin but the opening on the neck is kind of tight and around the waist and hips it is way too tight, so I sent it back.
It was not possible to just exchange it for another size, so sent it back and ordered XXL instead. Came within two days but still too tight. The sleeves felt longer but otherwise it was the same fit. Did not see any difference between XL and XXL, so I sent it back again. Will look somewhere else.