I highly recommend Preferred Doors. I recently purchased a gear and pulley replacement set for my 20 year old Craftsman belt drive 1/2 HP opener. The parts were very reasonably priced and of excellent quality. What set this purchase apart from others was that it included everything needed to do the job, gears, clips, bushings, spacers, grease... They also included very thorough details on how to replace the parts, reset the limit switches test the opener and reset the wireless openers.
I had just bought a new double-wide garage door, and looked at the rollers that came with it - looks like junk to me. I searched and found these, so as the installation happened, these rollers are in from the very start. Why wait a year or two and then replace the originals? Looking forward to a long smooth life from these!