This is US sizing product. Each size will be one size bigger compared to Japanese sizing.(ex. US-M = JP-L)/ ELEMENTAL LAYER, Finetrack's fundamental series of the foundational layer worn directly on the skin under a sweat- wicking, quick-dry, high-performance Base layer, protects your skin from sweat chill, wetness and stickiness. It is a highly recommended piece for all who are active in the outdoors. The highly stretchable soft mesh material allows a full range of body movement, providing a comfortable, stress-free, functional fit. Suitable for wear in all seasons, ELEMENTAL LAYER features an excellent balance between moderate warmth retention and rapid sweat removal. The durable water repellency has evolved to 80 points per 150 washes, and the fabric is treated with antibacterial and deodorant technology. When worn by itself, this ultra-thin mesh textile is slightly translucent. The seam at the waist is sewn on the outer surface for a gentle skin touch.