The Deviator is a great jacket for "tweener" conditions when you need more than a base layer but will be active. It breathes and moves well during activity. I've worn this jacket on cool, early morning runs and caught myself still wearing it hours later because it's so comfortable I don't notice it like I notice most other jackets. Casual wear and running are the activities I've used for so far. I look forward to wearing the Deviator for uphill skiing this winter. I'm 5'10, 155 lbs and the medium fits well.