Flexi-Overdenture Nickle Titanium - Refills - 6 per Pack6 Overdenture Posts, 6 Attachment Caps, 1 Primary Reamer, 1 Countersink Drill. Based upon a patented split shank post, the ball and socket attachment delivers all the benefits of the Flexi Post for highest retention of full and partial dentures. The attachment can be placed without lab assistance providing a simple, inexpensive overdenture at chairside.