Usually my puzzles are only available from my shop, but this time it's quite a bit different. I was sponsored to make one of my puzzles open source.
The first 4x4x6 cuboid was made in 2004 by Tony Fisher, based on an idea of Geert Hellings to modify a 4x4x4 to have two extra layers. Joshua has made a very generous offer and paid me to design a 3D printable 4x4x6, and make it open source.
So this is the result, an open source 4x4x6 puzzle: