Blox Racing BXPT-20253 High Compression Exhaust Valve Set for Honda B-Series DOHC Engine Blox Racing valves are stock-size but high compression Specially designed to increase intake and exhaust airflow through the cylinder head All valves are swirl polished, feature undercut stems and hardened tips All valves are treated with black nitride, which provides a more durable and smoother surface compared to chrome coatings Increases compression by approximately 0.3 points