The Foal Book is the basic registry for horses whose lineage would qualify them for entry in the Studbook at adulthood. Unlike the primary Studbook, there are no restrictions based on physical appearance or soundness. Some adult horses are not eligible for registration in the Studbook and may remain in the Foal Book. Reasons for permanent Foal Book status may include unacceptable white markings or soundness and conformational issues. Stallions who do not qualify for Approval may remain in the Foal Book permanently. The purebred offspring of Foal Book Mares, are eligible for Foal Book and later Studbook inclusion. However, any colts born of a Foal Book Mare may not be eligible for Studbook (approved) Stallion status.