The AviProtek pattern 211 has acid-etched visual markers on the exterior surface of the glass. While initially being conceived as a vertical design pattern it can also be used horizontally. This pattern has been tested by the American Bird Conservancy with a threat factor of 23, meaning 77 percent of the time birds will avoid a collision. The pattern also meets the industry-recognized 2 X 4 Rule. Pattern 211 can contribute to earning LEED Pilot Credit 55: Bird Collision Deterrence.