This Great Planes’ 1-Piece White Nylon Spinner with Aluminum Backplate.

FEATURES: White nylon 2-blade spinner.
Aluminum backplate.
A sturdy aluminum backplate holds the spinner in round, which means
it turns truer, with less vibration.
Spinners attach securely to backplate with the included screws.
One year quality guarantee.
INCLUDES: (1) Spinner with Backplate
SPECS:    Diameter:            3-1/4″ (82mm)

Backplate Thickness:   1/8″  (3mm)
Backplate Hole Diameter: 5/16″ (8mm)