Three separate gel packs at the foot, middle torso and upper torsosections, surrounded by high-density foam.Premium convoluted foam for excellent pressure redistribution and comfort16% thicker than standard gel foam overlaysNylon top cover with skid-resistant vinyl bottom coverFluid-proof coverFour elastic bands secure the corners of the overlay to the mattress44" x 76" x 3.5" (86.4 cm x 193 cm x 8.9 cm)