Peter H.wrote a review of Castelli Mortirolo Reflex Jacket - Men's on January 16, 2018
Familiarity: I've used it once or twice and have initial impressions
Fit: Runs small
On their website, Castelli says this jacket is good for cool/cold weather riding down to a range of 43-59°F. I tend to chill easily so I figured I'd try it out in temps a little above that, and to make sure I didn't get cold I wore a long-sleeve wool Castelli base layer. I live in an area with lots of rolling hills and went out for a couple of hours for a moderately hard ride. The temperature when I left the house was 47; when I got back it was 57. As it turned out, I stayed comfortably warm and actually got a little too warm on the hills. I probably could have worn a sleeveless base layer and been just fine.
Anyway ... I think I can validate that the jersey will perform as intended. With a long-sleeve thermal jersey underneath, I can probably get down into the middle to upper 30s!