Feature: 1. OE Number: The referencing OE number of this accelerator pump diaphragm are 16021‑393‑004, 16021‑393‑014, 16021 MC9 771. 2. Fitment: The carb accelerator pump diaphragm is a replacement for XL250R 1982‑1983, for CB450SC Nighthawk 1983, 1985‑1986, for CM450E 1983. 3. Function: The accelerator pump valve membrane could improve the acceleration efficiency of the carburetor, ensure the high efficiency of the engine. 4. Complete Accessory: Each kit contain all necessary parts, such as spring, O ring gasket, rubber tube and accelerator valve membrane for better performance. 5. Material: The accelerator pump repair kit is made of premium metal material, which has high strength, wear resistant, resistant to gasoline, ethanol and methanol. Specification: Item Type: Carb Accelerator Pump DiaphragmOE Number: 16021 MC9 771, 16021-393-004, 16021-393-014Material: MetalFitment:Fits for XL250R 1982-1983 Fits for CB450SC Nighthawk 1983,1985-1986 Fits for CM450E 1983 Fits for XL500R 1982 Fits for CB650 1979-1982 (Check rod length before ordering) Fits for CB650C 1980-1981 (Check rod length before ordering) Fits for CB750A Hondamatic 1976-1978 Fits for CB750F Super Sport 1977-1978 Fits for CB750K 1977-1978 . Package List: 4 x Spring4 x O Ring4 x Rubber Tube4 x Accelerator Valve Membrane Note: Please double check the part number of your item, matching information is for reference only.If you are unsure of the item, please contact us before buying to avoid unnecessary return, thanks!