Accessories for a homogenizer include beads, probes, rotors, and stands. Beads are used in a ball- or bead-type cell disruptor, also known as a beadbeater. They are placed in the sample container to mechanically break down cell walls to release the molecules within. Beads are available in various diameters and in materials such as silica glass, steel, and zirconia. Silica beads, also known as silica microspheres or spheres, are the most commonly used. For tougher tissue, steel or zirconia beads may be selected. A homogenizer generator, or probe, is available in sizes to handle different sample volumes and in styles such as saw-tooth, slotted, and flat bottom. Some probes have a rotor knife attachment to process fibrous samples. Stands may be used with certain homogenizers to allow hands-free operation.