In most AMS, ACE and MMU, spools works best when centered. The original universal mini spool adapter design keeps the minispool to one side creating an interference. Adding an additional Spacer cross (original design only calls for one) in place of the original design concentric ring fixes that issue. But removing the concentric ring means the mini spool is no longer centered axially. This adapter fits over the spindle side spool plate center to correct that. Works like a charm!