This is a Vortech 1-3/4" Aluminum Two-Blade Spinner from Dave Brown. FEATURES: Light-Weight Aluminum Construction Polished Aluminum Color Includes Four Plastic Backplate Bushings, So The Backplate Will Fit Securely Around Any Ordinary Crankshaft Designed for Two-Bladed Props INCLUDES: One Two-Blade Aluminum Spinner and Backplate One 5x12mm Cap Screw Four Plastic Backplate Adapter Bushings REQUIRES: Vortech Adapter Nut (see COMMENTS) 4mm Allen Wrench (for the cap screw) SPECS: Width: 1-3/4" Height: 1-11/16" Weight: .08 oz. COMMENTS: To Match the Adapter to the Engine, the Modeler Must Use: 1/4-28 DAVQ8428: for OS .25-.60, Supertigre .25-.60, Fox .19-.50, Enya .25-.53, K&B .19-.65, OPS .40-.60 5/16-24 DAVQ8524: for OS .61-.90, Supertigre .61-.90, Fox .60-1.2 7x1.0mm DAVQ8710: for Enya .35-.60, .60-1.2 Four Strokes (Non R Engines) 8x1.0mm DAVQ8810: for YS .90-1.2 4-Stroke, Enya 1.2R 4-Stroke, OPS Super .60 and .61 5-Port 8x1.25mm DAVQ8812: for All YS 2-Stroke The Stock Numbers Above Are For the Short Adapters. The Long Adapter is Only Required on Spinners Larger than 2-1/2". It is best to use the Longest Adapter Nut that Will Fit. BBS 3/13/99 ir/jl