BASE5 (also known as thicknet) is the original "full spec" variant of Ethernet cable, using special cable similar to RG-8 X coaxial cable. This is a stiff, 0.375 inch diameter cable with an impedance of 50 ohms, a solid center conductor, a foam insulating filler, a shielding braid, and an outer jacket. The outer sheath is often yellow-to-orange foam fluorinated ethylene propylene (for fire resistance) so it frequently is just called "yellow cable" or sometimes humorously "frozen yellow garden hose".