Dave Brown adapter nut is constructed of plain black, CNC machined steel. 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: OS Max .25-.60, SuperTigre .25-.60, Fox .19-.50, Enya .25-.53, K&B .19-.65, OPS .40-.60, Webra .28-.80.
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.