Petzl Shunt Rappel Backup Device One Size. Used below the rappel device the Petzl Shunt Rope Grab works as a rappel back-up and replaces self- jamming knots like the Prusik. The Petzl Shunt Rappel Grab works on single and double ropes. Specifications for Petzl Shunt Rappel Backup Device: Manufacturer: Petzl Color: Stainless Weight: 6.6 oz Fabric/Material: Aluminum Frame Rope Capacity: Single ropes 10-11 mm or double ropes 8-11 mm Features of Petzl Shunt Rappel Backup Device Easy to install on the rope Smooth clamping surfaces wont damage rope May be used on single or doubled rope Package Contents: Petzl Shunt Rappel Backup Device Petzl B03B: Shunt Rappel Backup Device One Size