Many variations of all these styles and designs have been produced under many brand names. The body of a resonator guitar may be made of wood, metal, or occasionally other materials. Typically there are two main sound holes, positioned on either side of the fingerboard extension. In the case of single-cone models, the sound holes are either both circular or both f-shaped, and symmetrical. The older tricone design has irregularly shaped sound holes. Cutaway body styles may truncate or omit the lower f-hole.