This sliding diamond and gemstone gauge folds to the size of a half-dollar. Conveniently measures round, marquise, and baguette stones from 1 point to 210 points (1/100 to 2.1 carats). Made of aluminum for long, durable service. Measurements are stamped the point system, a common way to calculate the size and weight of a diamond. This gauge is useful when you are trying to estimate the weight of a stone that is set in a piece of jewelry.