Features: 1. Double-acting handles are rigidly attached to contact pistons and are automatically self-centering. 2. Helps to quickly check holes, slots, and recesses up to 6 inches deep. 3. The ends of both contacts are treated steel and precision ground. radius allowing proper clearance over the smallest hole the gauge will enter, 4, Constant spring tension provides uniform contact pressure, 5, Super quality, high rigidity, good wear resistance, durable in use, Specifications: Material: Tool Steel; Measuring Range: 8-150mm; Accuracy: 0.1; Quantity: 6pcs/set(ABCDEF); Package List: 1 Set x Telescoping Gauge(6pcs) Scope of application: Telescopic spring plunger into the hole (or slot), can control the detection of the inner diameter, used with micrometer or caliper, with knurled locking device,