Only Boyd Galaxy deep fill, fluid dual lumbar mattress for adjustable firmness Suspension can give perfect contouring support to places like the small of your back. By varying the amount of water in each if the 8'' dual lumbar waveless mattresses are 3 other solid mattresses choices you can achieve differing firmness levels, allowing for personalized support on each side of the bed. The 4-point tethering system in all four corners prevents polyester fiber from shifting. You don't toss and turn because you are evenly supported and offers a deeper, more restful sleep so you wake up feeling rested and refreshed on Boyd Waterbed Mattresses.