These are Brass Threaded Inserts from Du-Bro.

FEATURES: Brass threaded inserts.
          The perfect way to put threads into wood & mount engines to wood
            mounting rails.
          Threaded inserts make a simple & effective way to make wing hold
            downs.
          These can be used where blind nuts are hard to fit.

INCLUDES: (4) Threaded Inserts

SPECS:    Thread Size: 8-32
          Length:      9mm
                                                                      kr3/17/03