Molded of durable, Resmer® plastic. Three tier, grid design. Autoclavable. Withstands most chemicals. Will not float or corrode in water baths. Letters and numbers on top tier for tube identification. Large end plates accept labels. Racks for 13 and 16 mm tubes hold 72 tubes; racks for 20 and 25 mm tubes hold 40 tubes; and racks for 30 mm tubes hold 24 tubes.