i just got back from a week in utah and i was very happy with the pirana. rappelling with a pack was no problem. this is a great descender with lots of options for a variety of friction for braking. it's super easy to use by providing the basic shape of a figure 8, but with added features to increase versatility. the little instruction booklet that comes with it has great diagrams on how to properly use it. the petzl attache locking biner is a very snug and perfect fit for this device.