Added a chamfer to help the belt drop into the groove instead of catching on the side and making clicking sounds.
UPDATED 23 March 2012
Print with 0.1mm layer height if you dare!
Use 0.5mm extrusion width, or adjust numbers in scad.
can be used to tune your E steps. if they won't fit together, E steps is too high. if they're loose, E steps is too low. They should click together firmly straight off the bed.
For extra points, your pair must able to be taken apart by hand with some effort when empty but become much tighter when you put the bearing in ;)