Use the SPI 13-978-2 Inch/SAE coaxial centering indicator set for accurately centering and positioning components in most machining applications. 0.0002″ Accuracy. The versatile indicator can be used at any angle while the dial stays stationary as the machine spindle rotates. Includes an indicator assembly with a 1.6-inch diameter dial. The indicator features a revolution counter with 0.0005" graduations for a 0.25 inch measuring range with 0-5-0 dial reading. Set includes 3 internal feelers, 3 external feelers, center point feeler, and a restraining rod. Internal feeler diameters: 2" long for 5/32" to 4-1/4" diameters; 4" long for 5/32" to 8" diameters; and 6" long for 5/32" to 12" diameters. External feeler diameters: 2: long for 0 to 4-1/4" diameters; 4" long for 0 to 8" diameters; 6" long for 0 to 12" diameters. 0.13" ball diameter. A fitted case is included.