This is a 9x7 Three Bladed Prop by Master Airscrew. FEATURES: Glass Filled Nylon Propeller NACA Airfoils True Pitch Accurately Balanced Greater Thrust at Lower RPM INCLUDES: One Propeller SPECS: Pitch: 7" Diameter: 9" Hub Thickness: 0.5" COMMENTS: PER MASTER AIRSCREW: All 3- and 4- blades props are balanced dynamically at the factory prior to drilling. The mounting holes are then drilled slightly off center, if required, to properly balance the propeller. As such, your mounting hole may be slightly off center. Master Airscrew assures us this is perfectly normal and will not cause any problems during usage.