Item Include: 6 Pcs Telescoping Gage Set. Including: 5/16"~1/2", 1/2"~3/4", 3/4"~1-1/4", 1-1/4"~2-1/8", 2-1/8"~3-1/2", and 3-1/2"~6". Material: Tool Steel Construction, chrome coating finish. Supplied with a blue plastic bag. Operation: Choose the desired hole gauge, tighten the locking device clockwise, and measure with micrometer or caliper to determine the final hole size. Advantage: This set is high performance solution for quickly checking the internal dimension. The rigid handle and double acting design can produce uniform contact pressure for more accurate measurements. Applications: Quick internal bore checks in engine blocks, cylinder housings, or gear boxes. Verifying hole sizes in machine housings, sleeves, or fixtures during setup or quality control. Inspecting internal diameters in manufacturing or assembly processes.