All 'Mechs weighing from 20 up to 35 tons are classified as "light". Their skeleton can only carry limited armor, but the higher efficiency of smaller fusion reactors means that light 'Mechs benefit from superior mobility. They are typically fast but lightly armed and armored. These 'Mechs are generally used as scout 'Mechs and anti-personnel units instead of frontline combat duty, but some are designated combat 'Mechs with relatively heavy armament. Their low production cost, high proliferation, and relatively good supply of spare parts meant that they saw widespread use throughout history in virtually any role.