The Wilwood Dynapro 4 kit for 1955–1957 Chevrolet Bel Air is listed with a 5 x 4.50in/4.75in hub fit and a D&S rotor option. This Dynapro 4 configuration is intended for Tri-Five Bel Air applications where that hub pattern and rotor style are required. The overview clarifies hub sizing and rotor type to help shoppers confirm compatibility with their classic Chevy front spindles.
Wilwood 55-57 Chevy Bel Air Dynapro 4 Kit, 5 x 4.50in/4.75in Hub - D&S