On the outside, the Helly Hansen H2 Flow resembles any other no-nonsense midlayer, with its shiny black water-resistant ripstop shell and pockets. Its interior, however, is a stark contrast: A multitude of variously sized holes have been punched into the red Polartec lining. When the jacket is fully zipped, these holes trap body heat. If you're too warm, open strategically placed zips, and cool off quicker than you would with a conventional jacket. It's ideal for when you're working hard one moment and sitting the next. [$175; hellyhansen.com]