Edelbrock 1464 Carburetor Step-Up Spring - Pack of 5 Contains one of each 3 Hg (blue), 4 Hg (yellow), 5 Hg (orange), 7 Hg (pink) and 8 Hg (plain) springs Provides optimum performance to the carburetor Used to fine-tune the carburetor Step-up spring is made of steel Provides optimum performance of your carburetor