The Perfex resistance activated release features a no look open hook design and interchangeable 3 or 4 finger extensions. The Articulating finger extensions have a 35 degree range of motion. The Perfex knob system provides infinite adjustability. Includes interchangeable 3 and 4 finger extensions, 3 trigger post lengths: 7/8", 1" and 1 1/8", small and large knobs and Trainer Lock pin.