This is an 18x10 Composite Propeller from APC. 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 18x10 APC Composite Propeller. REQUIRES: ALL props require balancing (use TOPQ5700). May need prop reamer, use GPMQ5005 (SAE) or GPMQ5007 (Metric). 9/32" + 5/16" Tubing for Bushing SPECS: Prop Diameter: 18" Prop Pitch: 10 Hub Thickness: 0.40" Hub Diameter: 0.8" Weight: 0.047lbs Engine Shaft Diameter: 1/4" sdw 4/22/02 ir/kh