The MTC Bio C3205-S ClearSeal 0.5mL Microcentrifuge Tubes come sterile with attached caps, non-graduated and are self standing. The MTC Bio C3205S tubes are made from ultra-clear polypropylene and assembled caps with silicone O-rings that assure a leakproof seal from -90°C to +121°C. All ClearSeal™ 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.