Excellent for stones of all kinds. Comes in a leatherette pouch. Its smooth action assures accuracy. This gauge is made to zero out when closed and open automatically. This assures a gentle force by the user when measuring soft stones or pearls. The dial features "zero adjust" and is accurate to 0.1 mm. Two models available with maximum opening of 10 mm or 20 mm. This gauge is compact and fits neatly into pockets or purse. GAU-146.00 also features a locking screw to hold measurement.