Caps "click" when closing and are still easy to open. Crystal-clear polymer facilitates visualization of samples. Graduations at every 100 µL for easy volume estimation. Temperature range from -80°C to +121°C - Boiling or freezing, tubes will not pop. 0.6, 1.5, 1.7 & 2.0 mL tubes are rated to 20,000 Xg. 5 mL tubes are rated to 25,000 Xg. Manufactured from virgin, medical-grade polypropylene. Certified RNase, DNase, DNA and Pyrogen-Free - Sterile formats are Gamma Irradiated.