This is an X-Long Propeller Adapter Nut from Dave Brown Products. FEATURES: Plain black, CNC machined steel construction. Use with 3-1/4" to 4" spinners. 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 1.08 FSR, FT-240, FT-300 and FR-300, K&B 1.00, Magnum XL-180AR, Enya VT-240 Twin INCLUDES: (1) Propeller Adapter Nut (1) Propeller Washer REQUIRES: 1/2" Wrench Spinner Cone & Bolt Backplate Propeller SPECS: Crankshaft Thread Size: 3/8-24 Nut Length: 1.625" 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 kr2/26/03