This thing securely holds, positions, and aligns the primary mirror of a Newtonian telescope.
This cell is designed around a 114 mm spherical primary mirror, since it's cheap enough to experiment with (around $40 for primary & secondary at this place: meridiantelescopes.com). Plus, a much larger mirror cell won't fit on the beds of most printers.
Scaling up will certainly require some design changes, since larger mirrors are much heavier. Larger mirror cells will likely require a bigger printer bed or a modular design (check out the multi-cell arrangements below). Even at it's current size it might warp.