Compact, Lightweight, Mid-line attachable, Ascender/Descender. This device is awesome. Super quick rappels, match it with a Hass knee ascender and a Pantene foot ascender and you will rocket up trees. I have read mixed reviews about this item but after using it for a little over a year now the bad reviews in my opinion are from people who didn't take the time to learn how to set it up properly. Shoot your line up and tie a basal anchor to an near by tree and single rope up and down or if you will need to advance your line. Shoot up and isolate your line tie a canopy anchor and ascend single rope then switch to a moving rope system and your set. I think my only gripes about it are the clip for the single rope system chest harness attachment are a little awkward to clip into. You get used to it pretty quick though. My only other complaint is that when climbing a really sappy Fir tree the device can get so gummed up it will not slide. It is made to pretty tight tolerances and I really don't know any other device in its class that would not suffer the same issues. Always good to have an emergency backup prusik just in case.
