This is an APC 10x4.7 Slow Flyer Pusher Propeller. This is a "Pusher" reverse rotation prop for use with electric applications only, not for gas use.
Specifications:
Hub Diameter: 0.50 in.
Hub Thickness: 0.29 in.
Shaft Diameter: 1/4 in.
Product Weight: 0.42 oz.