These quality spinners are manufactured by Mejzlik in the Czech Republic.
The screw holes have been drilled but the prop blade holes have not been cut. This means they could be used for two or three blade props.
The spinner diameter is 85mm (3.4") which suits most BJ Craft Models.
The back plate is CNC machined aluminium and has been lightened as can be seen in the picture.
Weight with screws is ~30 grams.