50mL Metal Free centrifuge tubes in recyclable fiber racks. Non Pyrogenic. Lot certified RNase/DNase free. Low Metal Certified to 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). 25 per rack. 20 racks per case. Sterile. Made in USA.