Great Planes ElectriFly Aluminum E-Spinner 1/4"-28 Adapter Adapter for use with 1/4"-28 prop shafts. Constructed of aluminum, silver in color. Includes: 1/4-28 Spinner Adapter (1), 30mm Socket Head Screw (1), 25mm Socket Head Screw (1), 20mm Socket Head Screw (1), 13.5mm Socket Head Screw (1)