This Is A Short Propeller Adapter Nut from Dave Brown Products.

FEATURES: Plain black, CNC machined steel construction.
          Use with 2-1/2" spinners and under.
          This prop adapter kit tightens the backplate and propeller onto the
            engine, then using a single bolt-on design, holds and centers
            each spinner perfectly on its baseplate.
          Will fit the following engines:
          Enya .35-.60, .60-1.20 4-Strokes (Enya Non-Reverse Engines)

INCLUDES: (1) Propeller Adapter Nut
          (1) Propeller Washer

REQUIRES: 1/2" Wrench
          Spinner Cone & Bolt
          Backplate
          Propeller

SPECS:    Crankshaft Thread Size:  7 x 1mm
          Spinner End Thread Size: 10-32
          Nut Length:              0.875"

COMMENTS: Although it will depend on the thickness of your prop and the
            spinner size, as a general rule, always use the longest adapter
            nut possible.
                                                                    JAL 4/28/99
                                                                          ir/jl
                                                                      kr2/27/03