Amazon.com: NACHEE Dial Indicator with Magnetic Base Holder Differential Backlash Gauge 0-1.0" Tester Gage Gauge Fine Adjustable Long Arm 0.001" Precision : Industrial & Scientific
SPI Intertest Mechanical Caliper Gage 2 to 2.8″ Inside Dial Caliper Gage 0.0005″ Graduation, 0.0015″ Accuracy, 3.3″ Leg Length, 0.31″ Deep x 0.1″ Wide Groove, Ball Contact Points - 15-514-3 - Penn Tool Co., Inc
GD&T, Groove ID checking by using Internal dial gauge caliper, Inner diameter by dial gauge - YouTube