The Groz Feeler Gauges are an indispensable tool in automotive, aviation, diesel, and farm equipment manufacture and also in jigs, fixtures, and in inspection jobs to measure the space between two points, the thickness of a gap, recess or other internal dimensions. . Each leaf is marked with its thickness, making it easy to identify the right gauge for the job. The lock nut ensures that one or more leaves remain securely in position and can be easily detached as needed. The set is provided with a protective holder, which helps preserve the trueness of the leaf edges and protects the gauges when not in use. With their accuracy and consistency our Feeler Gauges are especially useful in adjusting spark plugs, distributor points, checking bearing clearance, fitting pistons, rings and pins and gauging narrow slots.