They are designed to be exact replacements for your existing Holley 3310 model 4160 series carburetor, so they don't require any modifications to install them correctly. Manufactured from quality die-cast zinc with a gold iridite finish, this Holley replacement metering block will keep your carburetor running correctly.
This part is legal for sale or use on Emissions Controlled Vehicles, Uncontrolled (Non-Emissions Controlled) Vehicles, and Racing Use Only Vehicles because it does not affect vehicle emissions and is not covered by emissions regulations.