Corning® 15 mL clear polypropylene (PP) centrifuge tubes have traditional polyethylene plug seal caps and are bulk packed 50 per bag. Foam racks can be purchased separately. Please check our Technical Information Listing for information on the physical and chemical properties of Corning plastic centrifuge tubes as well as important suggestions for safe use. Black printed graduations and a large white marking spot Maximum RCF is 12,000xg Sterile, nonpyrogenic and DNase-/RNase-free 95 k PA (14psi) pressure tested