The Martin Tool Metric Check Nut Wrench - 13mm is crafted from strong, quality steel. It comes in both fractional sizes, ranging from 1/2" to 1-11/16", and metric sizes, from 10mm to 41mm. These versatile wrenches are ideal for a variety of purposes, including tightening check nuts, stop nuts, jam nuts, and hydraulic fittings. The smaller sizes make them perfect for service wrenches, also known as Thin Head Wrenches, which come with a 15 degree angled slotted opening. These specially designed wrenches are commonly used to service thin adjusting and lock nuts. This type of wrench is available in a sleek, industrial black coating and proudly made in the U.S.A.