Basecourse: 0-80mm in size. These are mixed rocks, sand and silty soils generally used as road base.
Armour Rocks: 500mm to 1000mm in size. These are used to prevent/mitigate erosions. Typically used as protection to canal banks and to armor shorelines, streambeds, and other shoreline structures for stabilization and is used in applications where its mass can provide scour protection from fast flowing waves or water currents.