The InnoMax Genesis 500 Reduced Motion Waterbed Mattress reduces motion to provide custom-tailored hydrodynamic sleep, resulting in the virtually perfect ear-to-ankle body alignment as defined by physicians and chiropractors for the ideal sleeping posture. This deep-fill InnoMax waterbed mattress, for use with a minimum rigid box or wood waterbed frames, performs best when filled properly, and the fill level is below the top of the safety liner. The G500 waterbed mattress, which provides true InnoMax SG1 full-depth flotation and reduced motion performance also includes a mid-body wave reduction system balanced more to free flow than waveless performance. Other features include 20 Mil premium vinyl, Contouring body profile low tension sleep Surface, 1" Double reinforced corners, 4-Way tethered support system, and T-Corner lap seam construction. The SG1 (Specific Gravity 1) Low tension mattress (LTM) surface features responsive levels of support for your body's varied levels of need; for the head, mid-body spinal, and leg areas. For near-perfect body alignment, the responsive give of the generously over-cut SG1 surface cradles your body while the interior elements provide complementary support. Additionally, the SG1 LTM surface eliminates the disruption of the other sleeper when one gets out of bed and with varying weights of sleep partners. NASA astronaut training is often done underwater as it simulates the effects of being weightless because the human body, comprised of 90% water, is in balance with the fluid environment. Just as babies are suspended in a gravity-neutral fluid environment until born, InnoMax SG1 hydrodynamic sleep mattresses truly offer flotation support as nature prescribes. The body can only be truly relaxed when muscles do not have to constantly fight the forces of gravity. SG1 fluid suspension evenly supports your body in gravity-neutral sleep and offers a hygienic environment as they are easily cleaned with an approved waterbed vinyl conditioner. Size: King