E-flite Brio 10 ARF - Manual (Page 41)

 7. Insert the 'hex to round' adapter onto the shaft.
Then, slide the 6mm washer included with your
gearbox onto the output shaft.
 8. Slide the propeller onto the gearbox shaft. Slide
the spacer included with the spinner onto the
gearbox shaft in front of the prop as needed.
Note: Two spacers have been provided that
are placed between the propeller and spinner
backplate. Use the thin spacer for low-pitch
propellers, the thick spacer for high-pitch
propellers. This will prevent the blades of the
propeller from contacting the spinner backplate.
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