Amazon.com: Aluminum Shell and Tungsten Steel Pointer Dial Indicator High Accuracy Dial Gauge with Large Dial 38mm for Measuring Narrow or Concave Objects, and Internal, External Diameter : Industrial & Scientific
Cylinder Dial Bore Gauge 2"-6"/0.0005" 5.9" Internal Measuring Engine Indicator – Tacos Y Mas
Indicator (distance amplifying instrument) - Wikipedia