petzl pirana descender d05 petzl the pirana is a canyoning descender for single or double ropes. it offers three different braking positions to choose from, according to the weight of the user, the rope diameter in use, and the terrain. for use with single ropes between 8 and 13 mm in diameter can be used on double ropes, but certain braking positions may not be usable depending on the rope's diameter.