I used Thunderhead 100s for a while and had good luck with them. Then I started using Spitfire 100s three years ago and they work great. Seven deer and seven pass throughs. You need arrow weight more than speed. A lot of people think speed is what you need, but if the weight is not there you will not get good penetration. Just think what would do the most damage, a VW bug hitting something at 65MPH or a big Mack truck hitting something at 45MPH. My hunting arrows with the Spitfire weights 439grains. Good luck on whatever head you use.