The Mountain Hardwear Micro Thermostatic is one of the two lightest insulated jackets we tested in 2015, with a light 40 g/m2 synthetic insulation. Without a hood or a chest pocket, this thin model works well as a mid-layer under a shell. We found it has good mobility and layers well due to the slippery liner fabric. The Thermostatic Micro includes a couple of small features that add an ounce or so but increase utility. The hand pockets have zippers to close them up and the hem includes an elastic cinch cord to seal in warmth.
For a warmer and more featured hoodless jacket at the same price point, we recommend The North Face ThermoBall Jacket, our favorite model for use a a mid-layer in very cold weather.