Class L planets range in age from 4 to 10 billion years. Their diameters range in size from 10,000 to 15,000 km. They are located in the ecozone region of a star's solar system, and have rocky, barren surfaces with little water. Their atmospheres are oxygen/argon with a high concentration of carbon dioxide. Lifeforms, if any, are limited to plant life. Class L planets are suitable for human colonization with some terraforming.