AH-Type Radius Corner Hex Body Inserts provide exceptional spin out resistance in punched hex holes and are recommended for use with mating thread-locking fasteners. The radius corners of these inserts expand and fill the corners of a hex hole. (These insert can help avoid stress fractures of your material and prolong punch and die life by specifying a radius corner in the hex hole.) These inserts are available with either standard Open End (as pictured), or Closed Ends for leakage protection past the threads. For complete weathertight security, we also offer a variation with a foam seal under the heading "Blind Threaded Inserts" in this section of the Encyclopedia.