The design was updated with the Whippletree Tensioner stl which has a larger slot that is cut out for a 3rd peg at the pivot.The Whippletree idea came from Steve Wood (Gyrobot) created triangle-shaped connectors that allow fingers to flex individually until they all meet resistance. http://www.thingiverse.com/thing:392970 https://www.youtube.com/watch?v=ch6IuaLgQxo This allows the grip to conform to the shape of the object being grasped.  With pegs made from 3mm filament serving as pulleys, this device simplifies Wood’s mechanism by replacing his small triangles with posts (pegs made from 3mm filament) that serve as pulleys. It works with the Raptor Adaptor https://www.youmagine.com/designs/the-raptor-adaptor-v1-0.   On 31 Jan 2015 removed the original design to avoid confusion.  This design allows use of a small zip-tie on the central peg.  The thumb should be tensioned separately, tied to a separate zip-tie.