Corning® 50mL clear polypropylene (PP) preassembled closed systems self-standing centrifuge tubes come with the advanced polyethylene CentriStar™ caps. The CentriStar™ cap has an 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 eliminated all seepage when used under recommended conditions. 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.