With layers of blended British wool and viscose, a British wool and mohair blend, a British wool, hemp and flax blend and a cotton, hemp and flax blend. The Sapphire mattress features 20,000 of our award-winning springs, including Cortec™ Quad spring system, multiple layers of HD 4,000 and HD 3,000 Micro springs. With an in-house woven FR chemical treatment-free mattress cover and four rows of side stitching, this Seasonal Turn mattress has a warming wool winter side and cooling cotton summer side.