3 New Plastic Gem Gauges. This is a new set of 3 gem gauges. These gem measuring gauge gives accurate measurements in millimeter and carat sizes. Each measures approximately 3 3/4" x 2 1/4" (95 x 56 mm). We work hard to update our descriptions and pictures of our merchandise. As part of a process of ongoing innovation by our suppliers, newer versions of the item shown may be shipped before we are able to complete an update. As a result there may be a slight variation in color and design.