<p>Castin gravel details including Gravel is sometimes distinguished from rubble, which is loose rock particles in the same size range but angular in shape. scale, widely used by geologists in the US, defines granular gravel as particles with a size from 2 to 4 mm (0.079 to 0.157 in) and pebble gravel as particles with a size from 4 to 64 mm (0.16 to 2.52 in) for more details of Castin gravel download Autocad file , cad drawing , dwg format.</p>