Originally bought the Perfetto ROS 2 Convertible and sized up to L (size chart 100cm chest) when mine is 95cm. The medium goes up to 96cm- but loads of reviews said to size up. The large was way too big all over. So, purchased an M in the original Perfetto, which apparently by design is tighter around the chest than the 2nd generation. However, it fits great, in fact it's still a little loose in the waist. I'm 84cm which according to the size guide M- is exactly what they recommend. I'm 179cm, 80KG. For Castllie leg warmers and bib tights I am large- mostly because my thighs are big, even though my waist and leg length could fit into M.
So, don't size up! I've used it twice so far at 4°C with a Core mesh 3 Castelli short sleeve base layer- Zone 3 HR was a little warm, but I do run hot. Wore it at 10°C no base layer and it dealt pretty well with heat regulation- I wouldn't use this in warmer weather than this. I am very familiar with the rear facing Gore Infinium 203 (Windstopper) fabric, looks and feels identical to my Gore Windstopper collection of cycling jerseys. The front facing Infinium is 205 and is very slightly brushed for warmth. I could easily use this jacket with a merino wool base layer into minus figures, guessing -5°C (like my other WS jersey/jackets), even though they recommend it at 4°C. Really like the thermal non-Infinium under the armpit; looks identical to the Nano Flex 3G on my bib tights. Don't mind the 2 rear pockets but would have preferred the 3 on the ROS 2. Little suspicious of why they didn't use YKK zips on the side 2 zips- 'MyZip' is apparently a premium Italian zip manufacturer- so I am guessing Castllie know what they are doing rather than skimping on saving pennies. Although I bought the Perfetto 2 Convertible in Electric Lime, I got a deal on the Perfetto Military Green; I like to be seen on the road, but I love the Military Green over the Electric Lime. I have a bright orange helmet and run powerful lights in the day time- even summer, so that counteracts the camo!

La Giacca è molto Elegante la utilizzo prevalentemente con una bici Gravel, la ritengo molto Pratica, Leggera e resistente al vento;
nelle giornate fredde e umide non ho avuto alcun problema, anche con pioggia leggera sono rimasto sempre completamente asciutto.
Consigliata

Provata subito appena consegnata , giornata con sole velato e un po’ di vento , temperatura c’è 9/10 gradi , l’ho indossata con una termica leggera , veramente perfetta, leggera e traspirante. Consiglio di prendere una taglia in più, solitamente io uso taglia S , la taglia M è perfetta

Same review as I wrote for my Aplha Ultimate jacket.
Absolutely perfect masterpiece! Keeps you warm and dry from 5-10 degrees as long you are constantly riding of cause. Love it. Also the design is great.
Dont buy too small. I am 1,78, 83 KG, muscular, bought XL, its almost too tight.

Tried today for the first time. I underestimated how cold the wind was on my road ride but the protection offered by this jacket saved me from being cold. Very breathable apart from one area where it touched my body.