Innomax genesis 400 gentle wave waterbed mattress reduces motion to provide custom tailored hydrodynamic sleep resulting in 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 minimum 9x48x84" rigid box or wood waterbed frames, performs best when filled properly and fill level is below the top of the safety liner. the g400 waterbed mattress, which provides true innomax sg1 full depth flotation and gentle wave performance also includes a mid-body wave reduction system balanced to more free flow than wave less 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,.