Concerning girth (circumference [around], NOT width [across])...

Very Small=<4.5"
Small=4.5"+
Average=~5"+
*Large (Above Average)=5.5"+
*Huge=6"+
*Gargantuan/Gigantic=6.5"-6.75"+
*Monster=7"-7.25"+

Of course, there is a limit as there is with everything... A "Monster girth (7"-7.25"+)" often numbs the walls of the vagina because of the monotonous all-around pressure (this also occurs naturally during child birth to aid in reducing pain)!