I re-built my upper furler a few years back. The ball bearings had elongated and were no longer spherical...causing it to bind a little while under load. I contacted Harken (262) 691-3320 and ordered out the following parts: MP-126, Ball Bearing-1/2in TOR (HSB17), and HSB205, Smalley Ring - WSM-106-S02. Total cost a couple years ago was about $37. With a little bit of patience putting the bearing in the track, I have an upper furler that now works great! Sorry, I don't have the part number for replacing the entire upper furler.