I'm not sure, but I'm suspicious about the bearing claim. All Speedplay Zeros/LAs I've taken apart and cleaned, regardless of model, have had the same number and quality of bearings. Tho I'm not sure I've worked on CroMo LAs. Perhaps there's a subtle difference in the cartridge bearings I missed, but I can confirm that CroMo and Stainless Zeros are identical internally. The X5 however, does have one less bearing. Also, the stainless spindle is 2mm shorter.