This is an APC 20x11 Electric Propeller.FEATURES: Composite propeller construction Thin propeller ONLY designed for Electric useINCLUDES: One 20x11 propellerSPECS: Center hole diameter: 1/4" Propeller diameter: 20" Propeller pitch 11COMMENTS: The propeller comes with five locating rings: .128 .158 .197 .237 .313 the locating ring combines with the hub to create a precision fit.APCPart APCLP20011E