Each impact-resistant 2 mL tube contains 2 mm yellow zirconia beads and 1.6 mm aluminum oxide particles. Matrix J tubes have pink caps. Zirconium oxide has very high density and high tensile strength and hardness, and is effective at breaking very tough and hard samples, including organisms within a tough or dense exterior matrix. This is useful in applications such as isolation of intact organelles, and super-molecular structures where lysis conditions necessitate high impaction but low shearing. The small size, and high hardness of the aluminum oxide component will also break bacterial spores or cysts inside infected tissue. The mixture of large and small diameter particles is also effective at "scrubbing" and lysing target cells that are fixed to a matrix such as tape-stripped skin cancer cells.