U.S.S., S.A.E. & Metric Bolt and Nut Gauge Excellent for sizing bolts, screws, nuts (USS, SAE, and Metric) and twist drills. Size bolt diameter by pushing bolt through the sizing holes. Also gauges hex nuts and washers (USS, SAE) while metric hex nuts and washers can be measured by holding them under the metric holes. The back of the gauge includes a feature for measuring US and Metric thread pitch. Special notches on the front of the tool allow you to measure flat head metal and wood screws. Made of sturdy, light weight green plastic that resists water, alcohol, oil, and grease.