The Humminbird AS EC QDM Ethernet Adapter Cable is an approximately 12″ cable that is required if you want Ethernet capabilities on a 700 HD Series Humminbird product. If you are connecting one 700 HD Series product with another 700 HD Series product, you will require two of these cables. If you are connecting one 700 HD Series product with either a 800, 900 or 1100 Series product, you will only need one of these adapters plus one of the AS EC2, 10, 20 or 30 foot cables. Software updates on some 700 HD and some 800, 900 and 1100 Series products may be necessary also.