Formula 4 (F4) is a recognized SCCA Pro class. The intent of the San Francisco Region Regional Only classification is to permit F4 to race under their specific F4 rules (Pro Rules) and compete as an F4 Class at eligible SFR Regional/Divisional race weekends.
Technical Specifications for F4 are defined in the US F4 Sporting Regulations – referencing the latest version found via SCCA Pro F4 Series rules. The latest version is on-line at: https://www.sfrscca.org/wp-content/uploads/2023/09/2018-F4-United-States-Championship-Final-012518.pdf
F4 will run as a Regional Only Class within SFR Regional/Divisional events, and these events are operated under the 2018 SCCA GCR. All requirements/rules identified in the GCR are governing, regardless of those listed in the US F4 Sporting Regulations. The GCR takes precedence where conflict exists.