Step 1: Print off the newest file from Thingiverse
I made it at Techshop (www.techshop.com) on their Replicator 2 (3D printer, in PLA with 3 shells and 35% fill). If you are curious about my design process, here is my first revision: http://www.thingiverse.com/thing:78964 Since then I have gone through different designs, and even an 8-position version! Ultimately, the design included an angled center wall, in order to bring the magnets closer to the sidewall of the 1.5 mL microfuge tube. This increased the speed with which the rare earth magnets can separate the magnetic beads for all your magnetics-based purification needs.