Cryo vials are designed for storage of samples as low as -196?C*. DNase, RNase, and Pyrogen-free. Radiation sterilized. Polypropylene vials feature a large white frosted labeling area, silk screen graduations, and a leak-proof High Density Polyethylene cap. Skirted base vials have an internal flat bottom. Star base and round base vials have an internal U-shaped bottom. Self-standing star base vials are designed for one-handed use with a support rack. *Not recommended for use in the liquid phase of liquid nitrogen. Can be used in vapor phase of liquid nitrogen.