Coolant, specifically the RED (ROJO) version in a 32 oz (or 1 gallon) bottle. Anti-Rust Formula: Designed to protect against corrosion and scale to extend the life of the radiator. All-Season Use: Formulated to help maintain a stable engine operating temperature throughout the year. Ready-to-Use: A long-lasting formula that is not an antifreeze, intended for direct use in the cooling system.