This is the 2" diameter Aluminum flywheel that comes with the Classic 3 Pole Monopole kit. This is for people buying the New Molded kit that does not come with a flywheel. Use Crazy Glue or Epoxy to secure flywheel on the end of the shaft on the front side of motor to give added weight to the rotor. Also makes for easier motor starting.
Note: Flywheel is NOT designed with holes for magnets. Aluminum Rotor for 3 Pole Monopole, which is machined with holes to accept up to 6 magnets, is sold separately here: