Goodyear's Two-Piece Assembly is a tire in two separate pieces—a casing and a tread belt—that offers increased ton-mile per hour. Goodyear says the assembly improves traction, handling and stability, compared to conventional tires. The two pieces have corresponding grooves that interlock during assembly and are held together by air pressure when the casing is inflated. Casing design improves bead durability and reduces sidewall deflection. Parts can be replaced independently as they are damaged or worn out, reducing cost and waste. The initial offering is available only in the 45R 57 size, and is significantly more expensive than competitive tires.