Ultra-clear polypropylene Packaged in resealable bags of 50 Leak-proof O-ring seal Sterile, RNase, DNase & Pyrogen free White printed graduations CellPro™ screw-cap microtubes come sterile, in a variety of sizes, cap configurations, graduation options, and even a loop-cap option for the 2.0mL version. Made from ultra-clear polypropylene, these screw-cap microtubes include assembled caps with silicone O-rings that assure a leakproof seal from -90°C to +121°C. All CellPro™ screw cap microtubes are sterile, RNase, DNase, & pyrogen-free and may be centrifuged at up to 22,000xg*.*Refers to liquids with a specific gravity of 1.0, using appropriate rotors, cushions, and adapters.