Don't use them!!!!!!!!! I've had my own person experience of them going all the way through a deer and not opening up at all. Then this winter a good friend of mine had the same thing happen. I also believe there was a couple of thread of guys on hear saying the same thing. I think if they get any condensation or any moisture on them when it is cold out they will not open on occation. If they do open they work great though. Just won't take that chance. Moved to slick trick and never going back to machanicals.