Description: 6Pcs 8-150mm Telescopic Adjustable Inner Diameter Hole Measuring Gauge Tool Set This Telescopic Inner Diameter Measuring Gauge made from high quality Carbon Steel , very durable and long service life. Nickel-plated finished. rigid handle with self centering feature for quick checking of holes, slots and recess up to 6" deep. The ends of both contact are head treated stainless steel and precision ground to a radius to allow proper clearance on the smallest hole the gage will enter. Constant spring tension gives uniform contact pressure. The telescoping gauges are used to measure internal diameter or internal through-groove of the workpiece by comparative method. Usage:Under uniform spring tension, the plunger of the gage expand from the center to the diameter of the hole or width of slot being measured and then locked in place by a knurled knob, the hole size is found by measuring over the two contact point with a micrometer or caliper. Specification: Material: Carbon Steel Color: Silver Dimensions: Size A: 5/16" - 1/2" ( 8mm to 12.7mm ) Size B: 1/2"- 3/4" ( 12.7mm to 19mm ) Size C: 3/4" - 1-1/4" ( 19mm to 32mm ) Size D: 1-1/4" - 2-1/8" ( 32mm to 54mm ) Size E: 2-1/8" - 3-1/2" ( 54mm to 90mm ) Size F: 3-1/2" - 6" ( 90mm to 150mm ) Measuring range: 8-150mm ( 5/16" to 6" ) Package Includes: 6Pcs Telescopic Inner Diameter Measuring Gauge