Coaxial cables have one conductor insulated with a dielectric material and then surrounded by the other conductor, usually referred to as the center conductor and shield.  Triaxial cables are specialized coaxial cables.  Coaxial cables consist of two cylindrical conductors with a common axis. The two conductors are separated by a dielectric. The outer conductor, normally at ground-potential, acts as a return path for current flowing through the center conductor and prevents energy radiation from the cable. The outer conductor, or shield, is also commonly used to prevent external radiation from affecting the current flowing in the inner conductor. The outer shield or conductor consists of woven strands of wire or is a metal sheath. Triaxial cables are three-conductor cables with one conductor in the center, a second circular conductor shield concentric with the first, and third circular conductor shield insulated from and concentric with the first and second, usually with insulation, and a braid or impervious sheath overall.

Important performance specifications to consider when searching for coaxial cables and triaxial cables include impedance, attenuation, outer diameter, and cable weight.  Characteristic impedance of a uniform line is ratio of an applied potential difference to the resultant current at the point where the potential difference is applied, when the line is of infinite length. Note that the term is applied only to a uniform line. Coaxial cable is such a uniform line. There are three main impedance groups in coaxial cable, namely, 50, 70, and 93 ohms.  Attenuation is the decrease in magnitude of a signal as it travels through any transmitting medium, such as a cable or circuitry. Attenuation is measured as the logarithm of a ratio. It is expressed in decibels or dB.  The outer diameter is the diameter of the cable including dielectric and jacket.  The weight of the wire is given in units of weight per distance.  Important cable construction parameters to consider include cable dielectric, cable shielding, cable jacket, and cable conductor.  Choices for coaxial cable and triaxial cable dielectric include polyethylene, fluorinated ethylene propylene, foamed polyethylene, and foamed fluorinated ethylene propylene.  Shielding is a metallic layer placed around an insulated conductor or group of conductors to prevent electrostatic or electromagnetic interference between the enclosed wires and external fields.   Cable shielding can be braid, drain wire, foil, and foil braid.  Cable jacket is a material having a high resistance to the flow of electric current to prevent leakage of current from a conductor.   The cable jacket on coaxial cables and triaxial cables can be ethylene propylene diene elastomer, mica tape, neoprene, polyethylene, polypropylene, polyvinyl chloride, silicon, rubber, Teflon^®, and Tefzel^® . (Teflon and Tefzel are registered trademarks of the DuPont company.) The cable conductor is a wire or combination of wires not insulated from one another, suitable for carrying electric current.   Choices for cable conductors for coaxial cables and triaxial cables include aluminum and aluminum alloys, aluminum clad steel, copper clad steel, and copper and copper alloys.

Conductor size is an important criteria to consider when selecting between available coaxial cables and triaxial cables. In North America, wire area is measured by the American Wire Gauge (AWG) to indicate conductor size. The AWG is used to measure certain conductors including copper. The higher the AWG number the thinner the wire. This is because AWG stems from a measurement that represented the number of times the copper wire was run through a wire machine, which reduced the diameter of the wire. Thus 24-gauge wire went through the machine 6 more times than 18-gauge wire.  Outside North America, countries measure conductor size by the size of the area of the wire, measured in mm².  Common features for coaxial cables and triaxial cables include dual cable construction, plenum rated, and stranded.  Common approvals given to coaxial cables and triaxial cables include CSA Mark, UL Listing Mark, and UL Recognized Component Mark.