Jaws for a secure and firm grip on the uppers of the famous Tactical 73 brand, both the standard and side-cocking versions. Used for disassembly and reassembly of the barrel, they are extremely sturdy, using the best technical polymers in my lab—but not excessively so! In fact, the purpose of this item is to protect the upper at all costs, even at the expense of breakage, because excessive force could irreparably damage the upper. At that point, it becomes clear that it would have been better to heat the Barrel Nut.