This is an improved version of my Inverted 1x2x3 puzzle. (see here for info on the previous version: http://www.shapeways.com/model/106599/inverted_1x2x3.html) The differences between the first version are that the pieces are more hollow (resulting in a cheaper print cost), the pieces have tolerance (no sanding is required to assemble the puzzle), the puzzle uses an improved mechanism that prevents pieces from popping out, and the center pieces no longer require a nut to hold them together (you just need a #4-40 screw to screw the centers together). Other than this, the two are identical.

See the twistypuzzles topic: http://twistypuzzles.com/forum/viewtopic.php?f=15&t=17926

Watch the Youtube video: http://www.youtube.com/watch?v=wGqbtiFhNqw&feature=player_embedded