In my experience Tesla clothing is always a good value solid performer. This top is no exception.
My regular fit is somewhere between XL and 2XL. I bought this in 2XL and it is snug but it is a compression top and so there are no surprises there. However, the fit it tighter than its counterpart in 2XL T-shirt, which is loose my comparison (that shirt is not much tighter than a regular T-shirt).
We have fairly mild Winters here with maximums most often in the mid-teens (Celsius). This shirt is perfect for wearing under a regular T-shirt during outdoor exercise. Keeps you warm enough but without overheating. Does the job that I envisioned perfectly.