Weather, location, and modifications to your bike can affect your jetting and this aftermarket main jet kit is a great item to have in your toolbox to help resolve lean or rich jetting issues with your carb. Jet sizes: # 140 145 150 155 160 165 170 175 180 185 These jets are for the following Mikuni performance carbs: Mikuni VM20 – 273 Mikuni VM24 – 512 Mikuni VM26 – 606 Mikuni VM28 – 418 NOTE: If you don’t have one of the genuine Mikuni carbs listed above, please do not buy this jet kit as there are no returns or exchanges on jets. These jets only work on genuine Mikuni carbs (they will not work on all the Chinese copies out there and none of the Chinese pitbikes come with a genuine Mikuni carb).