Celltreat 229411 Polypropylene Centrifuge Tube, Sterile, 15mL Volume, Re-Sealable Bag (Case of 500) Graduations on clear tubes are printed in bold easy-to-read black ink and are accurate to  2% Large white marking area provides excellent contrast for identification All tubes are manufactured from high quality polypropylene and have smooth, flat surface polyethylene (HDPE) caps Clear centrifuge tubes are available in sterile (gamma irradiated) or non-sterile pack options