The Marine Corps uses three squads per platoon (plus one platoon commander and one platoon Sergeant) and three fire teams per squad (plus one squad leader).

Each team contains:

1 Team Leader armed with an M-16A2* Service rifle with M203 grenade launcher attached. He is usually a Corporal or Lance Corporal. In formation charts he is referred to as TEAM. The Team Leader commmands the team and carries out tactical decisions. He uses the M203 to cover dead space (unseen terrain like a reverse slope) in combat. The senior Team Leader also acts as the assistant Squad Leader.

1 SAW gunner. He is usually a Lance Corporal. He is referred to as FIRE or, informally, the Gunner. He uses his Squad Automatic Weapon to lay down covering fire. As the second senior man on the team, he assumes command if the Team Leader is wounded or killed.

1 Assistant Saw gunner armed with an M-16A2 and carrying extra ammo and the spare SAW barrel. He is usually a Lance Corporal or Private First Class. He is referred to as ASSIST or, informally, the A Gunner. He changes Barrels for the Gunner and helps reload the SAW. He also takes the SAW if the Gunner goes down.

1 Rifleman Armed with an M-16A2. He is usually a Private First Class or a Private. He is referred to as READY. In nearly all team formations the READY is the Point Man. As Point he is the most forward member of the team, and thus the most exposed. He finds a trail or enters buildings first.

The order in any formation, for memorization purposes, is READY, TEAM, FIRE, ASSIST, however, their placement in the formation varies.
An example:

In the Skirmishers Right formation the order is, from left to right, READY (forward), TEAM (back), FIRE (forward), ASSIST (back).
If the formation were Skirmishers Left the Marines would be in the above order but from right to left.

*Some units now use M-16A4s or M-4s