stylistic:style_transfer, linguistic:paraphrasing
Franking privilege

In addition to this type of franking privilege, from time to time (especially during wartimes) governments and/or postal administrations also authorize active duty service members and other designated individuals to send mail for free by writing "Free" or "Soldier's Mail" (or equivalent) on the item of mail in lieu of paid postal franking, or by using appropriate free franked postal stationery. In the United States, unless otherwise designated, such mail is serviced by both the military and civil postal systems that accept them as First Class letter mail. In Mainland China, conscripts are entitled to the privilege of free postage on ordinary mail of up to 20 grams for personal correspondence from their units, which are stamped with a triangular red “Free Letter for Conscripts” franking.