RetroFilter air cleaners cleverly hide an LS drive-by-wire throttle body inside to maintain a low height and classic looks. Utilizing a hidden opening in the base to hide unsightly wiring from the throttle body, this trick air cleaner allows you to experience all the benefits of modern technology and keep the vintage look you want. Pair with any Holley intake manifold with a 4150/4610 square bore flange for maximum aesthetics and performance. The opening is 92mm but any 4-bolt pattern LS throttle body will physically fit. We recommend the LS2/LS3/LS7 style but the L33, L76, and L92 should also fit. *Requires adapter to connect to 4150/4160 square bore flange style manifold - Holley EFI part # 17-93 is recommended. All part numbers in this series: 120-500 - 16-Inch DBW Air Cleaner - Chrome 120-501 - 16-Inch DBW Air Cleaner - Black 120-520 - 14-Inch Dual Snorkel DBW Air Cleaner - Chrome 120-521 - 14-Inch Dual Snorkel DBW Air Cleaner - Black