I purchased this a while ago and have kept it in storage without ever using it. It's a backup rope clamp. This is a backup device for rappelling, set below the descender, and replaces self-jamming knots like the Prusik. It can be used with both single and double ropes. Setting it up is easy. The cam surface is smooth to avoid damaging the rope. It can also be used for rope climbing. Weight: 188 g Rope diameter: 10 - 11 mm (single), 8 - 11 mm (double) *Please refrain from purchasing if you are not serious about the transaction. Also, please refrain from purchasing if you are overly sensitive. Additionally, please consult with me if you are located in Hokkaido or any remote islands. Thank you for looking.