Sandboxx Letters is a paid service. Sometimes we have sponsors pay for your first letter to a recruit's Sandboxx profile, but otherwise each letter costs a Letter Credit. Each letter includes a pre-addressed reply envelope, a full color photo, and overnight tracking to most locations.
Letter credit pricing is detailed below:
USSA graciously gives each recruit one free letter credit on their account (when they sign up with a Sandboxx Address Card (SAC) when they arrive at boot camp. You do not have to be a USAA member to utilize the free credit. Whomever sends the recruit the first letter gets the free letter credit. Any letter sent after that must be paid for.