12 inch Hybrid Mattress in a Box, Gel Memory Foam and Pocket Spring ,Full Mattress

I bought this twin mattress for my class a motorhome has two twin instead of one double beds it was nice thick but it was a little off and doesn't quite fit Soo it is difficult at best to get sheets blankets so deep and too tight it overhangs and bunches the two corners and have to use a cake knives spatula to touch it in so fitted sheet unable to actually do more than shove it ramining it in the wall and ends causing one sheet to rip and one tear in comforter I have already had to flip it because the study not bed reinforcement isn't working since it is too big and wrinkles on two ends and long end there is bed rail it suppose to keep mayyeress form falling off but since size doesn't fit i am shoving it up best I can plus have built tn end table with lamps drawers adds to keeping mattress in place is causing structure of mattress mushed to the comfort is kinda lumpy but offered no other size nowadays not just four sizes and perhaps bunk bed even if smaller width because it has about inch or more length just that much to wide