It is convenient to categorize grain boundaries according to the extent of misorientation between the two grains. "Low-angle grain boundaries" ("LAGB") or "subgrain boundaries" are those with a misorientation less than about 15 degrees. Generally speaking they are composed of an array of dislocations and their properties and structure are a function of the misorientation. In contrast the properties of "high-angle grain boundaries", whose misorientation is greater than about 15 degrees (the transition angle varies from 10–15 degrees depending on the material), are normally found to be independent of the misorientation. However, there are 'special boundaries' at particular orientations whose interfacial energies are markedly lower than those of general high-angle grain boundaries.