One rack holds three different sizes of round or conical bottom centrifuge tubes. Holds four 50mL, seven 15mL and twenty-five 1.5mL tubes in the three different hole sizes (30.2mm, 17.3mm and 11.4mm respectively). The other rack holds two different sizes of tubes (six 50mL and twelve 15mL). Easy to assemble racks have a grid base with sides that fold up and end bars that lock into place securing the two rack decks. Dimensions are 246 x 104 x 64mm high (9.7 x 4.1 x 2.5"). The polypropylene racks are submersible and steam autoclavable to 121°C (250° F).