Add an extra shelf to BILLY bookcase to use it even more efficiently and fit more of your items that you want to store. This creates a new solution and generous storage when your needs and life change., Dark brown oak effect, 76x26 cm. Add an extra shelf to BILLY bookcase to use it even more efficiently and fit more of your items that you want to store. This creates a new solution and generous storage when your needs and life change. Particleboard.