INNOMAX Sanctuary Free Flow Full Wave Waterbed Mattress, Twin Sanctuary Free Flow Deep Fill Waterbed Mattress for full depth rigid side box frame Full Wave Performance and 20 year warranty No Wave Reduction and weightless feel featuring Full Motion Performance and gravity neutral fluid suspension mid-body support Zero wave elimination system and 20 mil premium vinyl Body Profile sleep surface generously overcut Low Tension Mattress design Double Reinforced Corners and T-Corner Lap Seam Construction Use with approved Waterbed Heater Waterbed Safety Liner Waterbed Water and Vinyl Conditioner Do Not Fill above Safety Liner