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, to be set below the descender, and it replaces self-jamming knots like the Prusik. It can be used with both single and double ropes. Setting it up is easy. The surface of the cam is smooth to prevent damage to 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 concerned about minor details. Additionally, please consult with me if you are in Hokkaido or a remote island. Thank you for looking.