I have the Assos 851 and wear it with nothing underneath into the mid 20F. The front is completely wind proof while the back allows your torso to breath. For winter apparel I think assos is more comfortable and tighter than the others that I have tried. For me having movement as unrestricted as possible and having my clothes fit me so they do not flutter in the wind is very important. There are some things where spending money is necessary, comfort in winter is one of them.

Don't you have any issues with the non windstopper on the lower part of the front. After riding less than an hour I am freezing in this part.

Do you ride in windy conditions?

I have recently bought an Assos 851 airjack and can't believe how warm it is for such a thin jacket. Beautiful fit, looks and feels like a jersey and so far I've worn it at 4 degrees C for four hours with a SS mesh baselayer no problems. Managed to find a ltd edition one with the piton green back so I'm not camouflaged with the tarmac

I also have the Assos 851, but to me it is not working very well. The jacket has a nice fit, but after high intensity sets, the jacket is wet from sweat on the lower part of the front, and with no windstopper I start freezing. Am I using this jacket the wrong way? I wear a long sleeved base layer underneath, and have tried with a vest on top to stop the wind on the lower part.