graybeard has it right...... the closer the imbalance is to the center of the shaft it's on, the less effect it has. spinners don't weigh much to start with, and their entire weight is very close to the center of rotation, so their impact on radial imbalance is negligible. add to that that the process of injection molding produces very even distribution of the plastic they are made of and an imbalance is hardly even probable, much less enough to e noticeable. if you are feeling an imbalance after mounting a spinner, check that the cone is not wobbling,...it's possible the "imbalance" is because the cone is not snapped down all the way because it is making contact with the prop on one side. I have had to reshape the cut outs for some props. as long as you keep the clearance around the prop reasonably even on both blades, there should be no noticeable imbalance.