Accessory 12-mm diameter red insert. Therack fits onto the Biomek 3000, FXp, and NXp workstations and holds various-sized polystyrene and polypropylene tubes, microfuge tubes and cryovials. To ensure proper tube fit, inserts must be used. Due to variations among manufacturers, tubes and cryovials should be measured prior to selecting an insert. Measure one inch from the tube bottom and select the insert with the appropriate diameter, or check for size using inserts from your starter kit. Order is one case of 25 12-mm diameter red insert tubes.