The Performance Tool steel construction caliper is the ultimate tool for precise measurements, up to 6 inches (150mm). Its quality steel construction ensures accurate inside, outside, and depth measurements, while the knurled thumb lock and sliding wheel make it easy to take and record measurements for later use. The smooth sliding action provides greater precision and control, ensuring that you get the most accurate measurements possible. The large open view window provides a clear sight of measurements, making it easy to read and record them. With a dual scale that provides standard measurements up to 1/16th of an inch and metric scale up to 1mm, this caliper is suitable for any project, big or small. Whether you're a professional or a DIY enthusiast, the Performance Tool steel construction caliper is a must-have tool for precise and accurate measurements.