One Well rack 

Move the wire and friction-fit rack to exactly where you need your tube. Friction-fit racks securely hold conical or round bottom tubes with 27.5 to 29 mm OD. Link the interlocking plastic racks to form a line of 50 mL tubes. Both the wire and interlocking polypropylene racks are autoclavable. Interlocking racks are sold in assorted colors of blue, green, yellow, pink, and orange.