Bonowi Smartlock 2 link chain handcuffs are extraordinarily heavy duty and well made. Certified to new very demanding German specifications. The handcuffs are made entirely of stainless steel with well rounded edges. The locks employ 3 independent pawls separated by 2 anti-shim bars and open with a unique triple bit key. There are keyholes on both sides of handcuffs and the single and double locks can be released by turning key in one direction. Double locks at edge of handcuffs are finger activated and inset enough that accidental activation is not a problem. Bonowi handcuffs bow shape will accommodate both small and large wrists. First notch inside perimeter: 9.5"; last notch inside perimeter 5.8". Weigh 19.7 oz. 2 keys included. Made in Germany