Never considered these, doubt I ever will. I do all my own refletching to the offset that works for my setup & broadheads. I wonder if the FOB's would get the arrow spinning as soon as offset vanes do. My biggest concern would be arrow penetration. Obviously it appears the FOB's come off the end of the shaft on impact, also taking your nock off. Regardless that alone would have to slow some penetration. I'm not for slowing any amount of penetration, regardless how small.