Socket head cap screws are the default bolt of choice on most karts worldwide. They're incredibly strong and feature hex sockets for the ability to really crank 'em up tight. If you're like most karters, your torque wrench is set to "tighten till it strips, then back it off a quarter turn". Seriously, don't do that. Tight's nice. Too tight sucks.
These bolts are measured from under the head of the bolt, to the end of the thread (ie, the head of the bolt is not included in the measurement). They have a 6mm hex socket.