MetalFree® microcentrifuge tubes. With flat easy open attached snap caps, side graduations, and frosted writing surface. Certified free of metals to 1 part per billion of 21 common metals. Protease, Human DNA, ATP, RNase/DNase and Endotoxin Free (non-pyrogenic). Polypropylene USP Class VI resin. Ultra high centrifuging to 40,000 x G. Freezable to -80°C. Autoclavable. Natural color. Capacity: 1.5 mL. 500 per resealable bag. Made in USA.