What does MIL-SPEC rated mean?
MIL-SPEC 810 is a rating system developed to determine how well a radio will withstand the rigors of cold, heat, dropping and vibration (among other things). The designations C, D, E, and F indicate the most advanced level of certification applicable to the radio with “F” being the most recent rating. Additional information is available at http://en.wikipedia.org/wiki/MIL-STD-810.