Prison gangs are criminal organizations that originated within the penal system and they have continued to operate within correctional facilities throughout the United States. Prison gangs are also self-perpetuating criminal entities that can continue their operations outside the confines of the penal system. Typically, a prison gang consists of a select group on inmates who have an organized hierarchy and who are governed by an established code of conduct. Prison gangs vary in both organization and composition, from highly structured gangs such as the Aryan Brotherhood and Nuestra Familia to gangs with a less formalized structure such as the Mexican Mafia (La Eme). Prison gangs generally have fewer members than street gangs and Outlaw Motorcycle Gangs(OMGs) and are structured along racial or ethnic lines. Nationally, prison gangs pose a threat because of their role in the transportation and distribution of narcotics. Prison gangs are also an important link between drug-trafficking organizations (DTOs), street gangs and OMGs, often brokering the transfer of drugs from DTOs to gangs in many regions. Prison gangs typically are more powerful within state correctional facilities rather than within the federal penal system.