This is an 8mm linear bearing to test Igus part RJZM-01-08 (http://www.igus.com/wpck/3663/drylin_r_rjum_01?C=US&L=en). The outer shell is printed in ABS and the inner sleeve is printed in Igus Iglidur 180-PF Tribo-filament. The Iglidur filament is made specifically to hold up to wear caused by repetitive motion. See here for more info: http://www.igus.eu/wpck/12019/iglidur_TriboFilament?C=DE&L=enFor the shell, I printed in ABS, 30% infill, 0.1mm layer height, 250 C nozzle, 100 C heated bed with a light coat of ABS slurry. The insert was printed using the same parameters as above except I used the Igus filament and 100% infill. I've included four versions of the sleeve. I've found that at 8mm ID, the sleeve needs a bit of sanding out. For me the 8.3mm ID sleeve fits snugly on an 8mm rod. You may need to experiment depending on your printing conditions.