These racks support cells with a minimum of physical contact. Only the corners of the cuvettes touch the racks, greatly reducing the chance of damage to cells. The two tier racks accommodate 12 cuvettes of 10mm lightpath and will not scratch quartz cuvettes. Made of polypropylene, which is steam autoclavable at 121°C (250° F). 6 per case. The F18516-0787 features Stack Rack® Test Tube Rack interlocking end plates for extra security when stacking.