For X-Large birds weighing between 1000-1600 grams or 35 - 56 oz: Large moluccan cockatoos, green winged macaws, hyacynth macaws * ESCAPE-PROOF! With other brands of harnesses, your bird can easily remove the leash and harness. The Aviator Harness keeps yourpet safe and secure. * Self-adjusting leash: Automatically adjusts from the chest to the back as the bird climbs and flies. Fewer pressure contact points on bird. * The strong steel slides have been powder-coated black to make them unattractive as toys. However, we have not heard of any bird yet that was able to break it. * Easiest to install - one piece design - No buckles or clips.