This board supports a circulation pump. Used in the following Sundance® models: 2008+ 1-pump 680 Burlington® model equipped with a circulation pump 2007+ 680 Hartford® and Hawthorne® models equipped with a Circulation Pump 2007+ 780 Hamilton, Chelsee®, Certa and Camden® (1-pump) 2005 - 2006 780 Series Sundance® Spas (Palermo, Bahia, Cayman) 2003 - 2005 Sweetwater Board (Palermo, Bahia, and Cayman) Replaces the 6600-087 and 6600-088 Board 3.56, with circulation pump systems. If your system has a 6600-087 and the EPROM chip that begins with a 5 (such as REV 5.54), then you have a 6600-287 board. Used in the following Jacuzzi® models: 2008+ J-375 2007+ J-365, J-355, J-345, J-335 2005-2007 J-325 (240V Model) 2002-2006 J-335, J-345, J-330, J340 2002-2003 J-325, J-320 2008+ J-230 with Circulation pump 2007+ J-280/J-270 with Circulation pump 2011 J-LX®/J-LXL® Replaces: 6600-288 6600-088 6000-167