Our bamboo-weave shirts feature a 70/30 blend of viscose bamboo with soft organic cotton fabric. This special blend lends a soft hand to these durable shirts, which naturally offer wicking, odor control and UV protection. Cut from 5.6 ounce mid-weight fabric, these shirts will do a better job of keeping you cooler, drier, warmer then your old cotton shirts. Bamboo is also a sustainable fiber (the fastest growing plant on earth) that requires little water, no pesticide, and produces more oxygen than trees. The bottom line... these shirts are good for you and good for the environment.