Use the Gravelometer Cobble Scale to grade or measure gravel and small cobble-sized sediments in the field. It’s easy to carry, measures stones far more accurately than a ruler, and meets USGS standards. Lightweight tool has 14 square holes of common sieve sizes, ranging from 2mm to 180mm. A scale, in 10mm increments, along one side can be used to measure up to 310mm. Dimensions: 11”H x 13-1/2”W.