The Marine Corps offers monetary bonuses for enlisted Marines who agree to re-enlist in "shortage" MOSs (jobs).
Zone A -- Marines who have between 17 months and six years of service at the time of re-enlistment
Zone B -- Marines who have between 6 and 10 years of service at the time of re-enlistment
Zone C-- Marines who have between 10 and 14 years of service at the time of re-enlistment

