I weigh 81 kilograms and I got the medium size (I am fit). It is tight-fitting and you feel like it bothers you in some movements, but it is tolerable. I am talking about the size.
As for the materials, they are of great quality and it does its job very well.

It does a great job as an inner fleece under the sweatshirt. Especially in humid and 5-10 degree temperature conditions, you can go outside and feel comfortable (always inside the sweatshirt). It should be noted that its size is slightly larger than I estimated (with the intention of buying it as a substitute for the thermal one, meaning I wanted it to be more fitted from the beginning), so I ended up going for one size smaller.

Height 175, weight 73 kilograms, excessively small - short to the point of being ridiculous (above the navel) and the sleeves are 10 inches shorter. I will try the L size, luckily it fits my wife who is exactly 170 and 62 kilograms, at the small end