This is the 2-Blade 3" Vortech spinner from Dave Brown Products. This attaches to the crankshaft of the engine on the front of the plane. FEATURES: Lightweight aluminum construction INCLUDES: One Dave Brown 3" (89mm) 2-blade Vortech spinner 4 prop shaft adapter bushings for different shafts REQUIRES: Prop adapter nut for specific engine SPECS: Length: 3-7/8" (99mm) Diameter: 3" (75mm) COMMENTS: A XLong prop nut is recommended for use with the spinner: X428-6428 1/4-28 XLONG fits: Como.19-.61;Enya.25-.53;Fox.19-.50;HP.21-.61; Irvine .20-.61; K&B .19-.65;OPS .40-.60;OS .25-.60 Picco .21-.45; ST .25-.60; Webra .28-.80 X710-6710 7x1mm XLONG Fits: Enya .35-.60, .60-.1.2 4-stroke (non-r engines) x524-6524 5/16-24 XLONG Fits: Como .75-.90; Fox .60-1.2; HP 1.2 4-stroke; OS .61-.90; ST .61-.90 X610-6610 6x1mm Long Fits: Enya .15-.25; OPS .65; Saito .30-.45 X810-6810 8x1mm XLONG Fits: Enya 1.2R 4-Stroke; HP 1.2 4-stroke; OPS .60, .61 5-port; YS .90-1.2 4-Stroke X812-6812 8x1.25mm XLONG Fits:OPS Maxi .30; Peco .60-.80; Rossi .40-.61; Webra .61-1.2; all YS 2-stroke mcw 4/27/06