MetalFree™ Conical Centrifuge Tube. 15mL. Sterile. With attached flat screw caps. Certified free of metals to 1 part per billion (1ppb) of Calcium, Magnesium, Zinc, Iron, Manganese, Copper, Aluminum, Silicon, Nickel, Vanadium, Sodium, Phosphorus, Cobalt, Chromium, Potassium, Lithium, Lead, Selenium, Cadmium, Mercury, and Arsenic. Additional heavy metals have been tested for using the prescribed USP method and confirmed to have levels lower than 1 part per million (1ppm). Caps are pure colorless natural polyethylene. Patented anti-smear writing surface. 3 color printed graduations and reverse reading scale. ATP, RNase/DNase and Endotoxin Free (non-pyrogenic). Validated Sterilization (ISO 11137) for use in Research and Medical labs. Polypropylene USP Class VI resin. Centrifuging to 17,000 x G. Freezable -80C. Autoclavable tubes. 50 tubes per bag/10 bags per case. 17mm W. 118mm H. Made in USA.