Features. The Rocker is a self-tailing rope access back up device and can be used handsfree when traveling up or down the rope. For use with single ropes from 105 127mm 38 12. For use without a shock absorber. Can also be used on a work positioning lanyard flipline. Thumbcatch can be used to park the device Specifications. Certifications CE EN3532 EN358 EN12841A. Strength MBS Dependent on rope type. Weight 164g 578OZ