This is a standard Holley Carburetor main jet kit, with thread sizes of 1/4 "-32 and jet hole sizes of 40,41,42,43,44,45,46,47,48,49. The quantity for each size is 2 pieces. You can get a total of 20 pieces.Made of brass and processed by CNC centers, the cumulative sales have exceeded tens of thousands of sets, and the product quality is trustworthy! 1/4"-32 UNF Unified Fine Thread If you need other sizes, please leave us a message after ordering, send an Amazon email, or contact the seller. The seller can then make the main jet according to your requested size and send it to you. We will provide you with excellent after-sales service. If you have any questions during the ordering process, you can contact us. Holley Carburetor MAIN JETS Sizes - 2 each 40-41-42-43-44-45-46-47-48-49 Holley Main Jets (20 OF THEM) 1/4"-32 UNF Unified Fine Thread Use In Street & Race Applications Fits Holley & Holley Style Carburetors Including AED, Barry Grant, Quick Fuel, Demon, Avenger, Etc.. These Will Come In A Plastic Storage Container (20 INDIVIDUAL JETS)