Yuil Model M-05 Stainless Steel Double Locking Thumbcuffs. Made in Korea. They can used as a lightweight backup for handcuffs. These thumbcuffs are unusual in that they have separate keyholes and double locks for each cuff. The keys have a single small bit. The cuffs will not open with standard Yuil keys or universal keys. Weigh 2.8 ounces.