It might look almost identical to the Petzl Croll but there are a number of subtle differences. The Basic is designed as a rope clamp style ascender - it slides along the rope in one direction and jams in the other. The Basic's cam teeth initiate a clamping action that pinches the rope between the cam and the frame. The cam has a slot for removing mud and bark debris. The bottom hole on the Basic is located on less of an angle to the Croll so it will not sit flat on the chest. EN567: 1997