I have run the Millville K771 on Zach's last two bikes. Pa trails are loaded with rocks and they hold up well. I like them because the terrain varies from mud, clay, soft dirt, hard pack, roots, and rocks. Other than the cheapo trials tire I have my my KDX (I like it more), the Millville tires have worked just as well as any other knobby I have used the last few years.