Each impact-resistant 2 mL tube contains one (1) 1/4" (6.35 mm) diameter Zirconium Oxide coated ceramic grinding sphere. Use to break hard/brittle samples. Specialty applications include RNA extraction from difficult samples where lysis by impaction only is preferable with minimal amounts of mechanical shearing. This grinding matrix is chemically inert and will not bind nucleic acids. Includes an additional bag of grinding spheres so that 2 ea can be used for very difficult samples.