The Haltec Large Bore Pencil Gauge is a precision measuring instrument used to check the diameter of holes and bores. It has a range of 1.000-6.000 inches, graduations of .001 inch, and includes 6 interchangeable anvils sized from 1-6 inches in diameter. The gauge is made of hardened stainless steel with satin chrome plating and has a knurled locking ring to hold the desired anvil in place. It features a friction thimble for fine adjustment and a flat base for stability. The pencil gauge allows machinists, toolmakers, and inspectors to accurately measure the size of holes, bores, and recesses for quality control purposes.