Tu Bookcases really hold up. Their coated metal shelves can withstand heavy items and adjust with minimal effort as storage needs change. At 15" deep, they easily house tools, personal items, and of course, books of any size. Eco-Friendly Description: Indoor Advantage Gold certification is SCS Global Services' highest level of indoor air quality performance for furniture. The certification ensures that furniture products support a healthy indoor environment by meeting strict chemical emission limits for volatile organic compounds (VOCs).