Twisted Chews Knot Ball is a durable knotted rope toy made from 100% premium cotton rope to keep pets playing safer and longer. Twisted Chews Knot balls have a strong center, so they're perfect for tough chewers. The rope ends provide for a great game of tug-of-war. Rope toys help keep your dog's teeth and gums clean and healthy. Unlike humans, dogs only have two cones in their eyes, causing them to see a limited pallet of colors. Blue is the darkest color they can see and yellow is the lightest. By making our toys blue and yellow, your dog sees great contrast and can find them easier.