The Hornady Neck Wall Thickness Gauge is a must-have accessory that complements the Hornady Concentricity Tool. This gauge offers measurements in 0.0005-inch increments to ensure the maximum level of accuracy so you can identify and correct variations in case neck wall thickness. The Hornady Neck Wall Thickness Gauge not only helps to measure the neck wall thickness to reduce variation, but it also helps you to verify the accuracy of your case neck turning projects. Simply put, when combined with the Hornady Concentricity Tool, this Hornady Neck Wall Thickness Gauge ensures the maximum level of accuracy possible.