An ultra-lightweight overlay mattress from conditioning sleeping gear series “AiR” for athletes. Sleeping on AiR LAYER overlaid on a bed mattress, your weight is distributed evenly. The core material is multi-layered woven fabric with original monofilament yarn of polyester. The fabric is swelled by heat-treatment; four corrugated layers are formed. Each monofilament yarn is planiform, so it’s hard to be buckled. Woven with thick yarns, the lower layers are harder. The yarns occupy mere 2% of this material’s volume, the rest 98% of that is occupied by air. This mattress is washable and fast drying. HARD and BASIC types are available.