The Chicago Model 1507 is a set of handcuffs that are Darby Style, an older variety that come in a fixed size and offer some limited movement. With this size restriction, however, comes the distinct advantage of requiring a special key that screws into the cuff itself to open. These cuffs are curved and offer very high-quality construction with a slick and polished silvery finish. Inside perimeter: 7 1/4". Includes two screw in keys.