Justin pretty much summed it up. They are excellent heads, accurate tough and very sharp. They are expensive but they work very well. I would rate them right along side the best heads avalible. Just to clear up a misconseption, the head does not spin in flight, but rather it will rotate once it makes contact with the animal. This spinning motion is supposed to aid with penetration, especially when bone is contacted. I can't say for sure how accurate or valid this is, but I will say I have yet to find anyone that has tried the heads and didn't love how they worked.