This two-piece long-sleeved pajama set is made of 95% Bamboo and 5% Lycra. They are very soft and luxurious feeling. Bamboo fabric is naturally antibacterial, antifungal and antistatic. Bamboo wicks water from the body 3-4 times better than cotton, keeping skin comfortable, rather than sticky in summer weather. And, Bamboo stays 2-3 degrees cooler in hot weather and warmer in cold.