Fitz-Rite test bars are made in the USA and are held to the highest standards for checking the accuracy of your CNC machining centers' spindle. They are manufactured from mill-certified hardened alloy steel. The shank is held concentric to the taper within one tenth (TIR .0001"). The taper is manufactured to ASME B5.50 standards and precision ground to meet AT-3 tolerance.
Test bars require a retention knob fitted to your machine specifications. Retention knobs are available for purchase separately.