The Mammut Eiger Free Light IN Vest fills with LOOPINSULATION, a recycled synthetic fill made half from industrial rope production offcuts and half from recycled PET. A 20-denier Pertex(R) Quantum Air shell blocks wind on exposed ridgelines while staying breathable enough for a strenuous bootpack. The chest pocket zips shut around the whole vest, turning it into its own stuff sack for the pack or a jacket pocket. What Our Gearhead(R) Experts Are Saying:"I stuffed this into its own chest pocket on the skin up and pulled it out the second we stopped on a ridge, and it cut the wind instantly without ever making me sweat through the climb beforehand. It's the first vest I've stopped debating whether to bring."