Manufactured using high-purity, virgin USP Class VI Medical grade polypropylene, these centrifuge tubes are free from natural rubber and heavy metal and conform to US FDA 21 CFR. Include leak-proof threaded HDPE caps that are free of added colorings and trace metals. A large, white marking spot allows you to easily label samples. MaxiRCF™ Trace Metal-Free Centrifuge Tubes with 20,000 x g maximum RCF work well for any high-density gradient separation. They are specifically manufactured to ensure that common trace metals and elements that can interfere with experiments are below an ICP-MS detection level of one part per billion (< 1ppb). Metals included in testing are: Zinc, Boron, Iron, Copper, Manganese, Aluminum, Silicon, Nickel, Vanadium, Phosphorous, Cobalt, Chromium, Lithium, Selenium, Cadmium, Mercury, Arsenic and Lead. Available in sterile and non-sterile versions. Sterile versions are validated according to ISO 11137 for SAL 10-6 and packed 25 tubes per sealed bag, 20 bags per case of 500. Non-sterile versions are bulk-packed as a case of 500 tubes. DNase, RNase, Pyrogen and latex-free. Manufactured using high-purity, virgin USP Class VI Medical grade polypropylene < 1ppb of 18 major groups of metals Certified leak-proof caps Allows frozen storage to -80°C