http://www.3riversarchery.com/schmeisser-archery-broadhead-one.html
I order most of my traditional equipment from Three Rivers. I think the single bevel is way over rated. It's like those fancy fish hooks that catch more fishermen than fish. Nothing wrong with them, but keep in mind that a single bevel has an angle 1/2 that of a double bevel. It's like those Lansky sharpeners where you choose a 20 degree angle or a 10 degree angle. If you sharpen from one side only you have a much finer edge. You can sharpen as fine an edge on a double angle, but you would never do it because it becomes evident the edge isn't as durable. I think it's a fad that will come and go. A lot of money for a lot of hype.
Espringers I had completely forgotten about some of those old single bevel broadheads. I think I may still have some. I know I have half a dozen original Bear broadheads left. I think I have at least 100 old broadheads kicking around from years ago. I shot a couple of deer with those back in the 1960's. They may rotate, but I think it's more in the imagination than actual performance. If you think about it there is no more real damage. Heck it may rotate just as it's coming to a big blood vein and rotation is causes it to miss the vein. Then you have to worry about matching the helical feathers with the head. I'm impressed, but not influenced.