Backcountry, backcountry, whatever The Atomic Hawx Ultra XTD 110 Boa GW boots took us there. These 110 Flex boots provide comfortable flexibility on the ascent and easy handling on the descent. and thanks to the Energy Backbone they provide sufficient stability at high speeds. Meanwhile, the 98mm diameter last prevents the sloppy feeling especially now that it is complemented by the BOA precision fitting system which locks the heel in place.