After extensive R&D and dyno/track testing with top engine and carburetor builders, R2C Performance has produced the best performing air cleaner system available for Holley 4412 and 7448 racers. More Horsepower and Mid-Range Torque. Offset forward to allow extra distributor clearance. Approximately 1/2" drop from carburetor sealing surface to the air filter surface. Precision Air Horn/Choke Tower Fit, No More Trimming and Grinding!!! Improved Airflow Characteristics. IMCA approved. Designed for maximum performance when using R2C Filters. Accepts standard 14" diameter filters.