Medium 20in EXTRA 3 Knot Tug. Mammoth Flossy Chews EXTRA rope toys are made from premium materials in fun shapes and colors dogs love. The outer core is made from a poly cotton woven sheath and the inner core is made from poly cotton woven fibers. EXTRA toys are tougher than our standard rope chews and made more durable for strong chewers. Rope fibers floss dogs teeth as they chew and play.