The Beal Gully Dry is twin/half certified at only 7.3mm. Comes in 50, 60,and 70M lengths. picked up a pair last fall, they seem to be the best/lightest ski mountaineering ropes now. For just rapping and cornice work you can go to smaller 6mm static lines, but I figured I'd let you know I've been stoked on the Beals so far.