ScrewSeal™ screw-cap Microcentrifuge Tube come sterile, in a variety of sizes, cap configurations, graduation options, and now light-blocking amber. 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 ScrewSeal™ 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. Ultra-clear polypropylene Molded or non-graduated options Leak-proof O-ring seal Light-blocking amber available Sterile, RNase, DNase, Pyrogen free Avaible 100 per bag, 10 bags per case.