The Parker kit number is #SK000097. The extra part is a seal spacer #31 on b/m. If it was used, it would fit in the ID of the seal spacer. The seal spacer is the new design which replaces the old seal and perimeter spring backup. Since my steering column stem has a small flange at the drive end, which sits on top of the bottom plate, the face seal at the bottom fits the OD of the steering stem flange perfectly. There must be some steering stems which do not have the flange, thus a straight shank with the drive lug, which would require this spacer for face seal centering. I used every part which was removed from the original column and the new face seal is the same thickness as the original, just a new design. The drive plate sits nicely on the seal and the thrust bearing. I'm sure there are different versions of these columns around, but wanted to check and make sure.