Bushings compatible with T-slot and V-slot wheeled carriages

If you went the cheap route for linear motion and got cheap nylon rollers that turned oval, you might like these -- in the same vein as the printed PLA LM8UU bushings, here are customizable bushings that you can use on your extrusions with any roller-carriage setup, whether they use an adjustment screw like http://www.thingiverse.com/thing:255756 or eccentric spacers like http://www.thingiverse.com/thing:902939.