Starrett S579HZ Self Centering Telescoping Gauge With 2 Telescoping Arms Set, 5/16"- 6" Range, 2-3/8 - 3-1/4" Handle Length (6 Pieces) Set of six telescoping gauges for measuring holes, slots, and recesses in woodworking, metalworking, machining, layout, and pattern-making applications Measuring range of 5/16 to 6" Two spring-tensioned telescoping plungers for uniform contact pressure Self-centering handles are rigidly attached to contact plungers Handles measure 2-3/8" and 3-1/4" in length Handles are rigidly attached to the contact plungers and are automatically self-centering Constant spring tension gives uniform contact pressure Both plungers are easily locked at any desired setting Ends of contacts are hardened and ground Set includes 6 gages with a range of 5/16" - 6" and case