15mL Metal Free centrifuge tubes with flat caps in bags. Non Pyrogenic. Lot certified RNase/DNase free. Ultra Low Metal certified 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). 25 per rack. 2 racks per bag. 10 bags per case. Sterile. Made in USA.