B-rated alpine boots designed for regular use with crampons:
B2 - Lightweight, walking/scrambling/climbing boots designed for use with C2-type (strap toe/clip heel) mountaineering crampons. A popular choice for winter hillwalking and regular scrambling in the UK, or summer alpine routes involving rock and glacier crossings.
B3 - Ridged, insulated mountaineering boots designed for use with C3-type (wire toe/clip heel) climbing crampons. A better choice for trekking peaks, alpine winter, and ice climbing.