Bottom line
SGLI is your low-cost group life insurance. If you are in the SELRES, you get full-time coverage and your premium is pulled automatically from your monthly pay. You can also add coverage for your spouse and children through Family SGLI (FSGLI). If your premiums fall behind, the Marine Corps can move to terminate your coverage, so keep them current.
What it means for you
If you drill in an SMCR unit or fill an IMA billet, your SGLI is handled automatically and the cost comes straight out of your pay. If you are in the IRR or doing short-duty stints, your coverage type depends on your status, and in some cases you have to pay premiums yourself. Falling behind on premiums has real consequences: it can block you from drilling or serving on active duty, and after a string of unexcused absences it can get your coverage cancelled. The piece worth knowing is that you can extend coverage to your family, and child coverage is free when your spouse is also covered.