Select among three one-well racks -- epoxy-coated steel wire racks, interlocking polypropylene racks, or friction-fit polystyrene racks. Move the racks to exactly where tube is needed. Friction-fit racks securely hold conical or round bottom tubes with 27.5 to 29mm OD. Link the interlocking plastic racks to form a line of 50mL tubes. Both the wire and interlocking polypropylene racks are autoclavable. Interlocking plastic racks are sold in assorted color packs of one each of blue, green, yellow, pink, and orange.