I first used fixed blade NAP Thunderheads and loved them so when i wanted to try mechanicals i went to the NAP Spitfires. Took 2 deer with them, no pass thru's with a 60lb bow on does but it poked halfway out the other side and the exit hole was huge. I bragged about these heads until I got a shot on the biggest buck I ever drew back on. 17 yard chip shot and I saw i hit above vitals but below spine, a high shot but with the angle I would have clipped something. BUT the arrow seemed to go in just a few inches. I don't know if the blade opened pre mature or if it hit bone but there was hardly any penetration. Didn't find a drop of blood. I was done with Spitfires after that. It could be a 100-1 shot what happened as Ive always been happy with Spitfires and NAP products in general but that one incident changed me. I now shoot Rage, I've taken 6 deer with them, unreal blood trails, easy tracking and no deer made it more than 40yds. Lots of opinions out there but thats my experience