Each impact-resistant 15 mL tube contains 1.6 mm aluminum oxide particles and 1.6 mm silicon carbide particles. Silicon carbide has relatively low density and high strength and hardness, and therefore is effective at breaking tough, hard, or brittle cell membranes. This is useful in applications such as isolation of intact organelles, and super-molecular structures where lysis conditions necessitate high impaction but low shearing. Matrix F is effective for applications such as RNA and protein isolation for samples in which Matrix A is too agressive. The irregular, angular shape of the Al2O3 and SiC crystals give lower shearing than the sharp edges of the garnet matrix.