This is an APC 20x13 Electric Propeller. FEATURES: Composite propeller construction Thin propeller ONLY designed for Electric use INCLUDES: One APC 20x13 Electric propeller SPECS: Hole diameter: 1/4" Propeller diameter: 20" Propeller pitch 13 COMMENTS: The propeller comes with five locating rings: .128 .158 .197 .237 .313 the locating ring combines with the hub to create a precision fit. ajw 8-25-03 ir/jxs