With layers of blended British wool and viscose, a British wool, hemp and flax blend and a cotton, hemp and flax blend. The Emerald mattress features 16,500 of our award-winning springs, including Cortec™ Quad spring system, multiple layers of HD 2,000 Micro, HD 2,500 Micro springs and Posturfil pocket springs. With an in-house woven FR chemical treatment-free mattress cover and three rows of side stitching, this Seasonal Turn mattress has a warming wool winter side and cooling cotton summer side.