Rota-Rack Tube Racks Rotate each of the four modules independently. Use several sizes of test tubes, culture tubes, centrifuge tubes, or micro-centrifuge tubes at the same time. Click each module into place, load with tubes, and carry! Rack maintains its orientation until you twist it again. Comes fully assembled. Autoclavable! Each module of the Rota-Rack for large tubes holds two 50 ml tubes, eight 15 ml tubes, six 20 mm tubes, or 10-13 mm tubes. Each module of the Rota-Rack for microtubes holds six 15 ml tubes, nine 1.5/2.0 ml tubes, twelve 0.5/0.6 ml tubes, or thirty-two 0.2 ml PCR* tubes or four 8-tube strips.