Highmoor 4pcs Telescopic Small Hole Bore Gauge Set 1/8"-1/2" Full Ball Type Gage Measure Tool 3mm-13mm & 6 pcs Precision Telescoping T-Bore Hole Gauge Gage Set 5/16" - 6" Range

Bore Gauge: Material: Stainless Steel Measuring Range: 3-13mm / 1/8"-1/2" Accuracy: 0.5mm T-Bore Gage: Material: Hardened tool steel Range : 5/16" - 1/2" , (8 - 12.7mm) 1/2" - 3/4" , (12.7 - 19mm) 3/4"- 1-1/4" , (19 - 32mm) 1-1/4" - 2-1/8" , (32-54mm) 2-1/8" - 3-1/2" , (54 - 90mm) 3-1/2" - 6" , (90 - 152mm) Constant spring tension gives uniform contact pressure Handles are rigidly attached to the contact plungers and are automatically self-centering Nickel-plated finished 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.