C660-HEF" High-Efficiency Chest -86°C Ultra-Low Temperature Lab Freezers. 660 L / 23.3 cft. 52000-sample capacity. New HEF Freezers from New Brunswick Scientific (NBS) reduce energy usage and operating cost by another 25% over the already industry-leading efficiency of our Premium models. For even further savings, 50Hz models utilize environmentally neutral, non-global warming hydrocarbon refrigerant, adding another 10% energy efficiency