Brass Millimeter Gauge This industry standard measuring gauge is always reliably accurate and will last a lifetime. 3-3/4" in length and made of solid Brass, this sliding gauge measures from 1 millimeter to 80 millimeters, and also measures inches from 1/16" to 3-1/2". Size 3-3/4" long x 1-3/8" wide. Why do I need this item? Without question, this is the single most valuable tool in your arsenal! Accurate and reliable, you will use it over and over again for years to come.