The stone and mounting gauge is an essential tool for jewelers and gemologists, designed with precision to measure both stones and mountings. It features holes for accurately determining stone sizes, with carat markings on one side and millimeter measurements on the other. The extensions are used to gauge mountings, ensuring compatibility with stones.

This gauge measures stones in 19 sizes, ranging from 1/32 to 4 carats in quarter-carat increments. For millimeters, it measures from 2 to 11 millimeters in half-millimeter steps. Made from durable aluminum, the gauge measures 4" x 4" (10 x 10 cm), providing both reliability and ease of use.