These are Great Planes' 1/4-20 Blind Nuts.

FEATURES: Metal construction with zinc plating to prevent rust from oxidizing
            on parts.
          The perfect mounting nut for hard to reach areas
          Perfect for engine mounting, landing gear, cowls, hatches, etc.
          Comes in a Parts-Pak clear plastic box with resealable lid
          One year quality guarantee

INCLUDES: (4) Blind Nuts

REQUIRES: 5/16" Drill Size
          CA Glue (GPMR6002)

SPECS:    Thread Size:  ¼-20