Petzl AscenTREE Double Ascender Books Making this part replacable is

Making this part replacable is a very good idea of Teufelberger and Treemagineers

Ventilation holes with sliding shutters allow the ventilation to be adjusted as needed from the outside

If you want to secure or block the choked sling

The rope now runs protected within the tube-shaped ring – and it might sound strange but it is true: The rope enhances the breaking strength of the ring and vice versa

Petzl AscenTREE Double Ascender Books Making this part replacable isPetzl ASCENTREE is a double handled, double rope rope ascender. This new device allows you to ascend a doubled rope with ease, making for easy footlocking. The design and materials of this product make it ergonomic and user friendly, adapted for intense use. Using the ASCENTREE with the PANTIN offers an alternative to the footlock.