3.0mm needle seat valve is what came in the majority of dirt bike carbs ranging from 65cc to 300cc two strokes.
Sprung 3.3mm 6 hole can be used for larger dirt-bikes such as a KX500 or CR500 that have substantial vibration.
2.0mm Viton is used in sleds, karts, etc. running gas with high flow pumps.
The 2.5mm steel tip is used for alcohol applications with high flow pumps. It is also used in sled demanding more gas with a high pressure pump
If you are still unsure of which to order, email sales@lectronfuelsystems.com with your application information including the model, fuel, and use.
Each needle seat valve comes with a gasket.