In the article, analysis of the work conditions and the metrological characteristics of the air gauges dedicated for the roundness assessment is described. To reach the required accuracy of the acquired data, the phenomena of gas dynamics had to be analyzed in the whole flow through elements of the air gauge. A model based on the second critical parameters was used, because it reflects the true processes of the air flow. As a result, fast and accurate simulations provided series of the characteristics to be considered. Nevertheless, the chosen air gauge configuration underwent the experimental verification of its metrological characteristics. Finally, the entire measurement system Geoform with the gauge head based on the chosen air gauges underwent the accuracy test in order to make sure of its overall measurement quality.