The bow "pro" at my bowshop said that the wing on the edge of these actually makes the vanes "lay down". He said that there's so much force on them that they actually bend over, decreasing the surface area, which is why you got them in the first place. He said they may make your arrow spin a little faster, but with decreased surface area in the back, it becomes less stable than an arrow at normal spin. (I wish I could draw a picture, it really does make sense!) So you're gaining spin, but losing stability, which isn't an even trade-off. Also, they are somewhat fragile compared to other fletchings. I'm shooting the Blazer Vanes, and they're really durable and I don't have any problems with accuracy.

p.s... Blazer Vanes in RED, WHITE, AND BLUE!!!!!!!!!!!!!!!!!!!!!!!(to remind me to give thanks to the men and women who make this country the best in the world, and giving us freedoms; like the freedom to hunt and enjoy life. just thought i'd throw this in here!)