the differences in the radial width of normal teeth along the arch of the teeth the outside dimension of the cross section of the inner tray 12 is equal to the inside dimension of the cross section of the carrier tray 14 when assembled the preferred embodiment requires no adhesive the assembly will stay together during heating handling and forming by way of friction forces in fig2 the inner tray 12 and carrier tray 14 are shown as a cross section though not to scale the drawing does illustrate that the wall thickness 29 of the inner tray 12 is less than the thickness 33 of the carrier tray 14 fig2 also illustrates the oblique angle between the inner side walls 20 26 and the bottom walls 16 22 at centers 28 and 30 the thinness 29 of the walls of the inner tray 12 is an important feature for the comfortable use ease of use and successful conforming of the inner tray or use while still producing an accurate hard flexible tray the thinness of the inner tray 12 because it loses the ability to maintain its shape at molding temperatures is a problem that is resolved by the double tray assembly set forth herein the carrier tray 14 although moldable.