They are good heads, but from what I have seen they require a bit more energy to use than some other mechanicals. Probably because they use friction to hold the blades in vrs a rubber band. I tried them to begin with and couldn't get pass throughs, neither could my buddy shooting an older darton set at 70 lbs. It didn't really make much more energy than my newer set up with a lower draw weight though. Both set ups were with arrows near 400 grn total arrow weight and shooting roughly 230 fps or so, maybe a bit less.

They worked as advertised though, opened up reliably and left a pretty large hole going in the deer. Shot just like my field points as well. I wasn't real impressed about tracking my first deer for 400 yards though. I took out one lung and the arrow stopped in the heart. I was 18 yards away from 16 feet up perfect broad side shot. I went to a fixed head and had no problems blowing right through deer. I also tried a mechanical with better penetration and they worked as well (Nail driver 2 blade heads).

I would say if you have well over 50 lbs of KE and a fairly heavy arrow they will work fine, if not you might want to consider using fixed blade heads instead.

Just my opinions though. I mostly hear good things about them.

Paul