The Rab Microlighter jacket uses TXdown sheet insulation in low-bulk baffles that sit flat against the body instead of puffing up the way loose-fill down often does. That flatter profile means it layers easily under a shell and compresses down small enough to stash in a pack or a jacket pocket. Articulated sleeves free up reach and mobility, built with climbing and bouldering movement in mind as much as trail miles. What Our Gearhead(R) Experts Are Saying:"I stuffed it into its own pocket between pitches and it disappeared into my chalk bag pack without adding bulk to my harness setup. That's the first down jacket I've climbed in without feeling like I was wearing a sleeping bag."