Rostock is a delta robot 3D printer. It uses 6 of these diagonal rods. The first version was using carbon tube and ball joints, but now these rods use universal joints and are fully printable.
Newer versions of the OpenSCAD source files will be published here: https://github.com/jcrocholl/rostock
Make sure you can use the full size of your platform. The rod length is 262 mm total (250 mm center distance of the universal joint M3 screws) and will fit diagonally on a 8x8 inch or 20x20 cm build platform. You may need to turn off "Skirt" in Skeinforge because the outline would be too large.
These rods printed very well in PLA with the following settings on my Prusa Mendel:
.35 mm nozzle at 185C
.2 mm layer height
.5 mm extrusion width
heated bed with blue tape at 60C
Send M106 to turn fans on while printing, to make sure the previous layer is cooled solid before the next layer is printed.
Turn off the heated build platform and let it cool completely before removing the rod, to avoid bending it while it's still soft.
If your printer is properly calibrated you should not need to predrill the holes for the M3 screws. Just screw them in, they are supposed to be somewhat tight for zero backlash. If you do need to predrill, use a 3mm or smaller bit. 1/8 inch (3.175 mm) would make the holes too big.
If your print bed is too small, you can print rod ends from joint.scad instead, and connect them with carbon fiber tube from the kite store.