After testing some 3D printed dice I discovered that square corners, not round or truncated corners, make the most balanced 3D printed dice. Also hollow centers were better than filled. So I made this. The square one scored a chi-squared of 14 after 30 rolls, the truncated one scored a 30, meaning the square corners is among the most fair 3D printed hollow dice I've tried. See http://joesmakerbot.blogspot.com/2013/10/testing-3d-printed-dice-fairness-chi.html for more infomation.