BLOX Racing composite velocity stacks are injection-molded from PA66 glass-filled nylon. Each significantly reduces the amount of heat soak absorbed by the velocity stack and then transferred to the air. The design and construction helps to reduce the overall weight compared to metal counterparts, which in turn, reduces the mechanical stress placed on existing air induction system and mounts.Pair velocity stack with BLOX Racing high performance air filter.SpecificationsNeck size: 4"Opening: 6"