Racks are shipped flat for easy storage. Easy to assemble: simply fold and snap together securely. Racks are autoclavable at 121° Celsius for 20 minutes. Can be used dry, wet or in water baths and will not float. Can be used in freezers without deforming or going brittle. Will not rot, rust or deform. Special design allows samples to be incubated at the same temperature. alpha numerical grid reference on top tier for easy identification of samples. Color coded for easy identification and bath work. Stackable when empty.