Choose from available size options. Medium foam and innerspring mattress. 9-in. thick with foam and individual steel coils. Quilted fabric cover. Individually encased steel coils isolate motion. 5-year manufacturer's warranty. The Lucid 9 in. Nimble Innerspring Mattress offers double the supportive comfort. This medium mattress features individually encased, high-grade steel coils that isolate motion and increase air flow. The coils are topped by a quilted layer of plush foam and a soft cover. This offers a medium firm mattress that won't sink and is incredibly soft. The bed is offered in a choice of available sizes. It comes compressed to reduce your shipping fees and offers an easy way to get your mattress through the door. Size: Twin.