U.S. Air Force Senior Airman Ruben Mejia, 1st Maintenance Squadron precision measurement equipment laboratory technician, uses gauge blocks to calibrate linear measurement tools at Joint Base Langley-Eustis, Va., March 17, 2017. The PMEL flight is divided in two main sections, electrical standards and physical dimensions, to support its customers. (U.S. Air Force photo/Senior Airman Areca T. Bell)