Corning® 15 mL clear polypropylene (PP) centrifuge tubes come with the advanced polyethylene CentriStar™ caps and are bulk packed 50 per bag. Foam racks can be purchased separately. The CentriStar™ Cap has a easy-on/easy-off flat top and offers advanced ergonomics with its wider knurls and roll-over edge design for easier gripping. This leak-proof design comes with a revolutionary plug feature that virtually eliminates all seepage when used under recommended conditions. Superior Performance Maximum RCF is 12,500 xg Temperature range from -80°C to 120°C 5 year shelf life Ease of Use Leak proof design Easy-on/easy-off cap Clear accurate graduations Large white marking spot Reliable Quality RNase-/DNase-free Heavy-metal-free color concentrate Medical grade polypropylene Nonpyrogenic Sterile