Yavuz Demirhan is a prolific Turkish puzzle inventor with nearly150 published designs at Puzzle Will Be Played ( http://puzzlewillbeplayed.com/-/designer/Demirhan.xml ). Tetradyma is one of his latest and is unusual in that it requires four identical pieces to fit into a cube shape. It is also printable without needing any support material. I would rate it as tricky but not difficult - a great design to give to novice puzzlers.The model includes a 0.1 mm offset and is based on 8 mm unit cubes. Although it could be scaled, be aware that this will change the tolerances and will affect how well the pieces fit together. I printed mine in PLA using 0.2 mm layer height, 0.4 mm extrusion width and 40% infill. I used Slic3r 0.98 and printed all 4 copies at the same time, using the More button.