The Shelton Series features a 360 degree foam encased posturized 540 Spectrum Coil System. This innerspring unit is designed to provide more support in the hips and torso to provide for optimal spinal alignment and a restful nights sleep. This series is available in 3 choices of comfort Firm, Plush and Pillowtop and may be ordered in a two-sided version as well. Firmness Firm Plush Pillow Top Euro Top Foam Encased Innerspring Construction Works in unison with various combinations of polyurethane. Foam Encased Six sided high density foam encased spring unit provides a true edge to edge sleeping surface. Spectrum Coils Spectrum Coils are soft on the surface and firm up as weight is applied for improved comfort balance. Heavy Duty Innerspring Built to last Our heavy duty innersprings are used in Hotels and Resorts all over the world.