This is a Master Airscrew Wood Props are made of Lightweight, Kiln-Dried Beechwood. Props with Larger Diameters Greater than 16 inches, are Made from Heavier Maple. FEATURES: All Wood Props, feature classic Squared Tips and Ample Airfoil Sections. The Latest in Engineering Technology used for this Updated Design. Lower Noise and Accurate Balance Available in a Wide Array of Sizes to Suit Every Application. Propeller is totally fuel-proof. INCLUDES: One 20x8 Wood Propeller SPECS: Center Hole Diameter: 3/16" approx. Propeller Diameter: 20" Propeller Pitch: 8" REQUIRES: Depending on the engine crankshaft size, the propeller may need to be reamed to a larger size using GPMQ5005 (SAE) or GPMQ5007 (Metric). COMMENTS: Four-stroke engines are typically higher torque engines and should use the larger props indicated in the range. Recommended prop ranges will vary depending on your particular engine and airplane. The Chart below represents average prop usage and should be used as Only a General Guideline. Always refer to the manufacturer"s instructions included with your engine. Engine Size 2-Stroke 4-Stroke .049-.051 5.5x4, 5.5x4.5, 6x3, 6x3.5, 6x4 N/A .09 -.10 7x4, 7x5, 7x6 N/A .15 7x6, 8x4, 8x5, 8x6, 8x7 N/A .20 -.25 8x6, 8x7, 9x4, 9x5 9x4, 9x5, 9x6, 9x7 .29 -.35 9x6, 9x7, 9x8, 9.5x6, 10x4, 10x5, 10x6 N/A .40 9.5x6, 10x4, 10x5, 10x6, 10x8, 10x9 11x6,12x6 .45 -.50 10x8, 10x9, 11x4, 11x5, 11x6, 11x7, 11x7.5 N/A .60 11x5, 11x6, 11x7, 11x7.5, 11x8, 11x9 11x8,11x9,12x6,13x6 .71 -.80 12x6, 12x8, 13x6, 13x8, 13x10, 14x8 N/A .90 13x6, 13x8, 13x10, 14x6, 14x8 11x9,12x8,14x6 1.08 14x8, 14x10, 15x8, 16x6 N/A 1.20 14x8, 15x8, 16x6 14x8,15x8,15x10,16x8 1.5 16x8, 16x10, 18x6, 18x8 N/A 1.8 18x8, 18x10, 20x6, 20x8 N/A 2.1 20x8, 20x10 N/A 2.7 -3.0 22x8, 22x10, 22x12, 24x8, 24x10, 24x12 N/A JAL 9/15/98 ir/jl