BB3 series is the most commonly used seal .it has BB3 series is the most commonly used seal .it has face is driven through the spring and 'L'-rings .highly recommended for duties with media containing solids eg.in waste water and sewage applications BB3 series seals include BB3 .BB3-2.BB3-3 BB3-2 is matched with lengthened bellow unit and BB3-3 with longer bellow unit