A small, 2-piece design that snaps together. I printed the prototype with 3 perimeters, 2 solid layers top and bottom, and 30% infill and it seems to be pretty solid. Printed easily with no supports, and with a 0.3mm layer height, it took about 18 minutes to produce. It works quite nicely with my Nexus 4 as well, so I'd imagine it's somewhat universal.