F Class: This is the very low end speeds of weaker characters such as humans (However, there are some beings who have this class of combat speed and are well enough above humans). Peak Humans and slightly above are the high ends of this tier and some might even able to reach at least Subsonic speeds (Up to Mach 0.8). D Class: Characters in this tier can reach the speed of sound. High ends can reach Supersonic speeds (Mach 1-5). B Class: In this tier, characters at the low end can reach Re-entry speeds (At least Mach 25) while thse at the high end are in triple digit Mach speeds.