Per the Manufacturer:The Starrett 443 Vernier Depth Gauges with Half Base, Micrometer Type, Inch, depending on the model, have a measurement range of 0 to 3", 0 to 6", or 0 to 9" ; a resolution (or smallest graduation interval) of 0.001", with + or – 0.0001" of accuracy. The vernier scale enables precise measurements in fine units. These gauges include 5/32" diameter measuring rods to cover the intended range. These units have two-inch long half bases that enable measurements of depressions close to shoulders and between obstructions. The bases and all measuring surfaces are hardened, ground, and lapped for accuracy. These gauges have a ring-type knurled lock nut and a combination ratchet and speeder to stabilize the gauge for precise measurements. These units include a protective case. Depth gauges are typically used in manufacturing, machining, and mechanical engineering.

Depth gauges are precision measuring instruments used to determine the depth of any shape that has a step, groove, or slot. These gauges often take the form of sliders that travel on a measuring beam or rods, are moved to position by hand, and then adjusted with a calibrated screw. The base of the gauge rests at the top of the shape whose recession is to be measured, while the beam or rods extend to the bottom of the recession to determine the measurement. Gauge position is read from a graduated scale, dial, counters, or an electronic display.

The L.S. Starrett Company manufactures precision measuring tools, metrology and testing equipment, and saw blade products. The company, founded in 1880, is headquartered in Athol, MA.

Measurement range of 0 up to 9", and resolution of 0.001"
Vernier scale for precise measurements in fine units
Includes adjustable, 5/32" diameter measuring rods to cover the range, one rod per inch of measurement
Two-inch long half base enables measurements close to shoulders and between obstructions
Bases and measuring surfaces are hardened, ground, and lapped for durability and accuracy