6pcs 5/16inch - 6inch Telescoping Gauges Internal Gauge Hole Gauges

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 : Letter Code Range Overall Length Depth A 5/16" - 1/2" (8 mm to 12.7mm) 4-3/8" 4" B 1/2"- 3/4" (12.7mm to 19mm) 4-3/8" 4" C 3/4" - 1-1/4" (19mm to 32mm) 4-3/8" 4" D 1-1/4" - 2-1/8" (32mm to 54mm) 5-7/8" 5" E 2-1/8" - 3-1/2" (54mm to 90mm) 5-7/8" 5" F 3-1/2" - 6" (90mm to 150mm) 5-7/8" 5"