Features: ➢ Spring loaded with locking knurled knob. Range: 5/16" - 6" (8mm to 150mm). ➢ Stainless Steel Construction, Titanium coating finish. ➢ Constant spring tension gives uniform contact pressure. ➢ Double action rigid handle with self centering feature for quick checking of holes, slots and recess up to 6" deep. ➢ Contact points are hardened tool steel and precision ground in the end measuring radius. ➢ Gage expands in a hole to be measured (locks in place and then removed to determine final hole size using a micrometer or calipers).