This is one R/C Airplane 16x6 APC Sport Composite Propeller by Landing Products. FEATURES: APC props are manufactured using a pultrusion process. This method causes the fiberglass "fibers" to be oriented axially in 1/2" long pellets, allowing for a higher fiber (60%) to resin (nylon binder) density. Providing substantially higher strength and stiffness than glass filled nylon. The additional stiffness is beneficial to control of vibration resonance response. The higher strength allows the use of thinner cross-sections, beneficial to weight and aerodynamic efficiency. Competition proven. Dark gray composite material. INCLUDES: One APC Sport Propeller REQUIRES: 9/32" + 5/16" Tubing for Bushing ALL props require balancing (use TOPQ5700). May need prop reamer, use GPMQ5005 (SAE) or (Metric). SPECS: Prop Diameter: 16" Prop Pitch: 6 Hub Thickness: 0.60" Hub Diameter: 0.9" Weight: 0.0708lbs Engine Shaft Diameter: 1/4"