- 12 Inch Twin Mattress. - Overall Dimensions: 75"L x 39"W x 12"T. - Description CHEVNI Mattress used independently-wrapped coils to ensure motion isolation, and a support layer of high-density foam to prevent sagging and rolling. Combined Innerspring and Foam Support - Independent pocketed spring design ensures that your body weight is evenly absorbed and distributed comprehensively from head to toe throughout the mattress. The high-density and gel memory foam combined bring cozy comfort and su