Personally customize your advanced massage features! The back inserts are available for almost all Lumispa models, excluding 601. The design of the Lumispa hot tubs pays special attention to massage features. When purchasing the hot tub, you can affect the number of jets and massage features with individualized back inserts. Choose the best massage features in accordance with your personal preferences! The back inserts are available as three different options: Whole back massage with particular attention to the upper back and shoulders. The insert has 12 x 2” jets. Effective massage evenly for the whole back. The insert has 6 x 3.5” jets. Versatility with different-sized massage jets. Effective massage especially for the lower back. The insert has 2 x 2” jets, 6 x 3” jets and 2 x 5” jets.