The LINENSPA 12 Inch Gel Hybrid Mattress is the softest mattress in the LINENSPA line and sleeps cooler than standard memory foam. It combines the conforming properties of memory foam with cooling gel to disperse heat so you can rest easy. 12 Inch and More. You may have missed out some of the informational pages I have included and jumped straight to this section – 12 inch memory foam mattresses. .