that the top wall 38 of the plate 32 is flush with flange 30 of the cover 22 this way the maximum use is made of the space made available by the recesses of the food tray covers without increasing the overall size of the insulated container this flush relationship of the top wall 38 of the plate with the flange 30 of the cover also insures contact of the plates 32 with the bottoms of the trays when the trays are stacked in an insulated container having supporting strips on the inside walls for engaging the flanges of the trays for maintaining hot foods above a det the temperature maintaining material should be a fusible substance having a high specific heat and a high total latent heat with a melting point at or above the det of the food preferably a the fusible substance is a petroleum wax the thermal characteristics of petroleum waxes vary depending primarily upon the oil content of the wax the characteristics affected by the oil content include the total latent heat the heat of fusion the specific heat both in the liquid and solid states and the melting point the following table shows the thermal characteristics for typical petroleum waxes available from i g i boler petroleum.