Easy to adjust: Suitable for precise measurement. Professional precision inside diameter measuring tool! Easy to use: The handles are rigidly attached to the contact pistons and are automatically self-centered, to achieve a perfect fit with the hole. Check the holes precisely: Double-acting rigid handle with auto-centering function allows for quick checking of holes, slots and indentations up to 6 "deep. Advanced design concept: Both contact ends are in Stainless steel treated with a head and precision ground on a radius to allow adequate clearance on the smallest hole the gauge will enter. 6pcs gauge set: 5/16 "- 6" (8mm - 150mm): Gauges 8-12.7, 12.7-19, 19-32, 32-54, 54-90 and 90-150mm. You can measure different sizes of holes with this inside diameter measuring tool. Specification: Material: hardened tool steel Color: silver / p Interval: 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) Usage: Under uniform spring tension, the gauge piston expands from the center to the diameter of the hole or the width of the slot to be measured, then locked in place by a knurled knob. Hole size is determined by measuring the contact point using micrometer or gauge. Package Included: 6pcs x Precision Telescopic Gage (packed with bag) / p Note: Please allow 1-5mm errors due to manual measurement Item color displayed in photos may be slightly different on your monitor since monitors are not calibrated same.