This is a 5.5x4.5E thin Composite propeller from Advanced Precision Composites. These are for use on electric powered aircraft only (not for glow engines).

• FEATURES:
  Gray composite propeller blades that assemble onto a propeller hub.
  Adaptable to different shaft sizes with the two adapters.

• INCLUDES:
  One composite propeller
  Two composite adapter rings
  One instruction sheet

• REQUIRES:
  Assembly onto motor or gear drive unit in your electric plane.
  Balancing

• SPECS:
  Diameter: 5.5"
  Pitch: 4.5"
  Hub inner diameter: 0.25"