The Men's Fission SL Jacket is the lightest weight, fully waterproof, fully insulated jacket that Arc'teryx offers. Perfect for all your technical, cold weather needs.... but I can't stop thinking about how great this winter jacket would be at a tailgate. Standing by a grill in style and warmth, eating burgers, drinking a beer or two and listening to the game. Or high-alpine mountaineering, trying to drink a completely frozen beer or two. The shell is waterproof/breathable GORE-TEX® and the insulation is Arc'teryx exclusive Thermatek™ (non-quilted, it eliminates cold spots). The laminated pit-zips facilitate effortless venting and temperature control. From the mountain top to the parking lot, the Fission SL will get the job done.