These Vortexer Attachments securely hold either a maximum of 8 or 20 microcentrifuge tubes, 1.5ml capacity, in a disk for simultaneous vortexing. Tube contents are mixed by holding the shaft vertically or at a slight angle with its end against the rubber pad or test tube cup of a vortexer. The 165mm (61/2") long shaft has a 25.4mm (1") diameter ball handle. Made of polypropylene with a Delrin® shaft. Packed per each.