That setup with a thermal underneath is good well down in to the 30s.  I save the leathers for sub-30s.

Winter motorcycle riding….  just as warm as a leather jacket but way less bulky than one!

Just got my vest today.  Love it!  Wasn't sure how sizing would work out but it fits perfectly over my Super Black Riders Jacket..

For reference.. 6'0", 175 lbs.  Size 40 vest, size 42 riders jacket.