I'm building a laser cutter but can't fine any suitable roller for normal t-slot extrusion, so I made one
OD24 x ID16x W10.5 (mm)
12/08/2016: v1.1 now printed seem fine but support is needed, my printed does not printing this properly yet on the bottom layer, OD increased to 24mm
13/08/2016: V2 final!! printed both with and without support both seem fine (depend on your printer)
Infill does not matter I guess raft is a must!