This is the APC Electric 11X5.5 RC Plane Propeller

Thin Electric
Use LPAR06E adapter rings
Includes one set of rings from LPAR06E

Pitch (inches): 5.5
Propeller Diameter (in.): 11
Hub Diameter: 0.80 in.
Hub Thickness: 0.41 in.
Shaft Diameter: 1/4 in.
Product Weight: 0.81 oz.
Color: GREY