RG-58/U is a type of coaxial cable often used for low-power signal and RF connections. The cable has a characteristic impedance of either 50 or 52 O. "RG" was originally a unit indicator for bulk RF cable in the U.S. military's Joint Electronics Type Designation System. There are several versions covering the differences in core material (solid or braided wire) and shield (70% to 95 overage).