Geotechnical Gauge Geotechnical Gauge Gauge has the following data:roundness chart; chart for estimating percentage composition; unified soil classification system; 6 common Munsell soil colors; soil compaction tests for clay sand; and sand grain size classification with actual sand grains from coarse to silt. Compact waterproof gauge fits in larger pant pockets or neatly into backpack. Nylon lanyard to attach it to notebook or clipboard. Has inches (up to 6") and millimeter (up to 110mm) ruler on one side. Perfect for geologist, mineralogist, soil scientist, archaeologist, ecologist, botanist, or any other field scientist!