A tire comprises several components&colon; the tread, bead, sidewall, shoulder, and ply. The plies were turned up around the steel wire beads and the combined tread/sidewall applied. Sometimes the inner sidewall contains information not included on the outer sidewall, and vice versa. Extrusion is also used for sidewall profiles and inner liners. This reduces rolling resistance by reducing sidewall stiffness at the cost of reducing damage protection. Bulges and depressions in the sidewall are such defects. A slot is cut in the sidewall to allow coupling. The pocket is the leather or nylon mesh attached to the sidewall and scoop. The pressure rating of tires is usually stamped somewhere on the sidewall. Tires with very little rubber, if any, covering the sidewall are called "skin wall". Tractor tires have high sidewall ratios for that reason. The head is made out of compact plastic where the mesh, sidewall and pocket form. In the middle of the other sidewall, a doorway led to the inner courtyard. One type of sidewall cores is percussion cores. Lock E17 at Little Falls has the tallest sidewall height at .