Smooth-action adjustment knob makes it easy to dial in the precise size of your fastener. Once you're dialed in, a stamped SAE rule (1/16" scale) and an open-extent tic mark on its head let you know exactly what size the fastener is, making it easy to switch to a socket, box, crescent... whichever spanner you feel is the best tool for the job. The wrench's I-beam handle is also stamped with its max-opening-size in both SAE and metric units, helping you to grab the right tool off the pegboard or out of the toolbox. Strong, reliable, forged carbon-steel wrench is chrome-plated to ensure rust-resistant longevity.