Due to the amazing efficiency of our HeatLock® system, in warmer summer environments we will often see spas maintaining 40ºC (100ºF)temperatures. These doors release some heat from inside the cabinet to moderate water temperatures. Specify the 8' door for all 8' Arctic Spa Models from 2000 through current. Specify the 7' for all 7' Arctic Spa Models from 2000 through 2006. From 2007 through current the 7' models use the same door as the 8' models. These doors are designed for the cedar cabinets.