Fowler Universal 3D Mechanical Sensor 53-710-175-0 Fowler's Universal 3D Sensors, made in Germany, are very accurate and versatile and available in both mechanical and digital models.3D Mechanical Sensors The 3D sensors are easily clamped into the milling spindle for exact positioning of the spindle axis on the edges of the workpiece or jig. Clamping shank diameter: 34" Accuracy: .0004" (with short sensor) Length without clamping shank:4-12" Short sensor insert diameter: 0.2" Long sensor insert diameter: 0.4"