The Fowler 54-554-730-0 electronic internal caliper has a plastic electronic housing with steel arms and hardware, an LCD readout, zero-setting capability, a hold feature, and is spring-loaded. This caliper measures IDs for hole diameters and groove diameters. The digital single-value readout LCD shows inches in decimals or fractions, or metric for versatility when measuring. The knurled lock nut holds the spring-loaded sliding jaw in position and helps ensure a consistent measurement. The measuring gages arms and hardware are made of steel for durability. The inside electronic caliper gage also has a reach of 4" and has an on/off/set and hold function. An automatic shut-off feature turns the caliper off after four minutes to prolong battery life. The unit also comes with a plastic case and instructions. Fowler, an American company, manufactures premium inspection and measurement instruments like electronic indicators, calipers, bore gages, and micrometers. The company, founded in 1946, is headquartered in Canton, MA.