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 has a 20000 Cortec™ Quad spring system, contouring HD 4000 and HD 3000 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. British Wool & Viscose Blend, British Wool, Hemp & Flax Blend, British Wool & Mohair Blend, Cotton, Hemp & Flax Blend, HD 4000 Micro Springs, HD 3000 Micro Springs, Cortec™ Quad Pocket Springs