I realize everyone's body is different and we all have our own comfort threshold when it comes to temperature, but fwiw I find the Assos Airjack 851 too warm once you get into the high 30s (F). For me with just a base layer the Airjack is good down below freezing, add a middle layer and it's good into single digits. But at 40°F the only way I'd wear an Airjack is if I were naked underneath, and it wasn't zipped up!


More internet anecdata: For every person I've come across who raved about their Assos Fugujack, I've probably come across 6 or 7 who claim it's too warm for 99% of the winter riding they do.