For a ripping 130-flex boot, the Hawx Ultra is mind-blowingly lightweight—Atomic’s lightest alpine boot to date, in fact. The brand achieves this by reducing the overall thickness of a standard boot wall. Don’t fret, as an insulated liner ensures your feet remain toasty, regardless of wall thickness. Atomic does, however, utilize a stiffer PU plastic for reinforcement in key spots—the heel, inner and outer arch—of the two-piece shell for better power and support. The boot also features a reinforced, asymmetric backbone made up of stiffer polyurethane plastic for added power and control.