The 400SX Super Waveless Hardside Waterbed Mattress features softer support, ideal for someone who wants the classic feel of a waterbed but doesn’t want any wave. The support system is made up of three mid-body fiber layers which provides extra support for the lumbar region. The 400SX model has:
•  A full, 9 inch depth for maximum flotation and minimum displacement between sleepers of different size
•  Tethered Wave Control Systems keep the wave control/support system in place and prevent shifting of those materials
•  Main seams are recessed completely underneath the mattress to eliminate flexing and stress on those seams
•  A black bottom panel made from a special vinyl formulation that is better at withstanding heat from the heater
 
The 400 SX Super Waveless Hardside Waterbed Mattress utilizes Sterling’s Premium 24mil Endura3 Vinyl. Endura3
is formulated with the finest resins available and is engineered to be the best material possible, making for a durable, long-lasting, high quality waterbed.