This is One R/C Airplane 20x8 APC One Piece 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. Single piece propeller. INCLUDES: One APC Sport Propeller REQUIRES: ALL props require balancing (use TOPQ5700). May need prop reamer, use GPMQ5006 (SAE) or GPMQ5007 (Metric). 9/32" + 5/16" Tubing for Bushing SPECS: Prop Diameter: 20" Prop Pitch: 8 Hub Thickness: 0.50" Hub Diameter: .9" Weight: 0.045lbs Engine Shaft Diameter: 1/4" kr4/17/02 dew5/8/02