Aeronautical Accessories offers a complete line of branded windows for MD 500, 520, 530 Series helicopters. All Replacement Windows and Special Use Windows are fabricated using state-of-the-art manufacturing processes, from high-quality acrylic and are FAA/STC approved. Effective 500E Model S/N 230 and subsequent, 520N and 530FF Model S/N 60 and subsequent (with one-piece lower windshield)