Tried several others and reached this one. Light and Comfortable. Since its excellent ventilation, I'm using this base layer below 15 degree by changing middle and outer one.

Prodotto ottimo per le uscite inverali. Accoppiato con 2nd layer e’ perfetto

Got the Flanders long sleeve, not because I live in Flanders, but because it is perfect for the conditions here. I use this with a Perfetto down to 4 degrees and not too hot up to 10 or even 12 degrees with the Pefetto side vents open. At a push I'd use it down to O with the Perfetto if I was putting in effort and generating heat. I use it with the Alpha RoS jacket when really cold, under 4 degrees and the weather looking like it might turn worse. I've used it sub zero with the RoS jacket and no doubt it would go much lower with it. I have not yet found it too warm and it transports moisture away well. Perhaps if you were riding particularly hard, it may feel a little warm, but for Zone 2 base rides, it is perfect across a wide temperature range and feels surprising comfortable. It is an extremely flexible base layer for me.

Honestly, this is warmer than I expected. For cycling I'm not wearing this too often (it doesn't get cold enough here, the PERFETTO alone is enough). That being said, I am loving this for my early morning runs, and the few days when it's cold enough. It's form fitting, and the vents for the sweat do help a lot. Definitely my favorite warm base layer.