The 7. 9 Dry Climbing Rope is Black Diamond's skinniest line certified for both half or twin use. Exceeding UI's standards for water-resistance, this rope excels on ice climbs and glaciated mountaineering missions, and still performs on traditional, rock, and alpine routes just as well as Black Diamond's non-treated 7. 9mm option. Just like every BD rope, this one has a middle marker safely setting rappels.