I see a lot of people saying to measure your filament and use that number, I have had better printing performance not doing that. I honestly have no idea why. The few times I have measured and used those numbers I end up with over extrusion. It's important to recognize that all filament has different tolerances. The Filament I sell has a diameter within +/-0.10mm and roundness of +/-0.07mm and you should find the same to be true with any high quality filament. Before I found a good source of filament I bought some stuff on amazon with poor tolerances. The biggest problem I ran into was filament that was thick enough to jam my extruder.