Mattresses Foundations Semi-Flex Steel Foundation Heavy Duty Steel construction for heavier mattresses also for longevity for those with a more active lifestyle wink wink nudge nudge . Mattress Border Arabella Profile Height 9 Foundation Twin SFD-1010 TWIN $95.00 Foundation Full SFD-1030 FULL $120 Foundation Queen SFD-1050 QUEEN $133 Foundation King SFD-1020X2 KING TWIN XL PAIR $198.00 Foundation TwinXL SFD-1020 TWIN XL SINGLE $99.00