JE Pistons SRP Pro 2618 line expands on the premium features of the SRP Pro series with the addition of extremely strong, 2618 forged aluminum material. All piston kits include gas-nitrided, carbon-steel pistons rings, pins, and locks. SRP Pro 2618 pistons maximize piston strength and maximize value, whether you?re building rowdy small block or a flame-spitting big block. As with all JE Pistons products, SRP pistons are made 100% in the USA.