by Dr. Ashby, page 23, http://www.tradgang.com/ashby/single-bevel-broadheads.pdf ... When using a single-beveled broadhead, remember to always make the arrow's rotation in flight match the bevel-induced rotation. This means right wing fletching with a right single-bevel, like the Grizzly; and left wing with the left bevels, such as the Abowyer. If you fail to do this, a double-be'like-broadhead' will out-penetrate the single bevel.