U.S. Patent # 4,474,573 (Open Patella). The exclusive PRO design, unique enough to receive a patent, makes this the most comfortable sleeve yet developed. Geometrically opposed seams provide a bent-knee configuration while eliminating bothersome popliteal irritation. The comfortable controlled tension fit of the sleeve makes it ideal for all-day wear. Made of a thicker ¼” neoprene for addition heat retention and support with the addition of a patella opening for better patella control. Available in beige or black, N1 or N2. Please visit our website at www.proorthopedic.com for size charts and measuring instructions.