Skunk2 Racing Steel Spring Bases for Honda’s H22A and F20B engines are designed to allow all H style VTEC cylinder heads to accept our high-performance, Pro Series Valve Springs and Titanium Retainers originally designed for B Series engines.Each Spring Base is manufactured using the latest 3D CAD (Computer Aided Design) and FEA (Finite Element Analysis) to make sure the design is optimized for strength and longevity. Engineers then test and prove the design on the engine dyno. Once approved for manufacturing, engineers make sure to only use high-quality steel that’s been ultrasonically inspected and certified. After CNC machining, each Spring Base is then individually inspected to ensure proper dimensions and that it’s free from machining defects. ONLY Use with Skunk2 B Pro Series Valve Springs in H VTEC engines.