The lightest down layer in our long history, this instant warm-up is the ideal down weight for layering or packing. The adaptable design features a layerable and athletic cut that allows the critical insulator to function expertly as a mid, last or emergency layer. 800 fill power premium European goose down traps core heat, while a water-repellent shell sheds precipitation. Stretch panels add mobility when reaching, twisting or turning, while a StormRepel® DWR sheds light precip and light snow from the surface. "I did not take this shirt off for three weeks in Antarctica. Slim enough to wear close to my body, unbelievable movement under other layers, and soft enough to sleep in at night. One of my new favorites." - Peter Whittaker