FiiO FT1 Over Ear Closed Back HeadphonesAmerican black walnut solid wood cups The FIIO FT1 cups are made from carefully selected FAS grade American black walnut*. The woods smooth grain unique to each piece and delicate texture truly showcase its natural beauty. This highly dense solid wood also helps to reduce cavity resonance effectively and minimizes standing waves. Nanowood fiber composite diaphragm The FIIO FT1s diaphragm primarily consists of carefully selected paper wood fibers,