The Blue Star mattress, preserves the natural curve of the backbone with high density foam layers and the DHT Spring system. The summer side features moisturizing cotton fabric, while the winter side features warm, 100% Woolmark® wool. An indispensable Yataş Classic, Blue Star...The Blue Star mattress, featuring the DHT spring technology with Yataş Exclusive, double heat-treated steel springs, defies wear for years. Woolmark®, 100% natural and the purest wool in the world, breathes, relaxes the heart rate and regulates body temperature.