The second photograph illustrates the haircut at the sides and back. A couple of people have written in questions to me asking about what to say to a barber to describe the haircut they want. Well Marcus (an 8 year US Marine Corps veteran - Semper Fi!) in the picture above writes to me with the following information:
"The haircut I usually get is known as a "Low-Regulation", but better known as "Low-Reg". It's basically just going around the bottom edge of the hairline and graduating it from 0-3 inches (maximum top length for modern Marines)."