This is a Petzl SHUNT. It's a backup device for rappelling that's set up below the descender, replacing friction hitches like the Prusik. It can be used with both single and half ropes. It's particularly useful in alpine climbing when using double ropes, in case of problems during rappelling that require ascending back up. Setting it up is easy. The cam surface is smooth to avoid damaging the rope. It's a used item, but has been used only a few times. There may be minor scratches or dirt from storage, but it functions well. Please refer to the photos for the appearance and condition. We are looking forward to your purchase if you understand that this is a used item. Applicable rope diameter (mm) Single rope: 10 < φ < 11 Double rope: 8 < φ < 11 #Petzl #petzl #Descender #Ascender #Rappelling #AlpineClimbing