Mad Max is a tattoo and piercing studio in Finland. They're famous for being the home of Samppa Eerola, piercer extraordinaire, who made his name in the business by doing quality piercings and designing new styles of jewelry. Quickly gaining in popularity today is his Mad Max bar, designed to connect multiple surface piercings with one piece of jewelry.
The Mad Max bar is a long piece of surgical grade steel that has been bent into a square zigzag shape. So far, Samppa's created two versions: the 4-point and the 8-point bar. The numbers refer to how many vertical sections there are per bar (if the bar is laid out horizontally; see visual aides below). A 4-point bar is usually around four or five inches long, and an 8-point bar can be around eight inches long, but since the jewelry is custom-made it can be any length. It's hard to find a part of the body to put an eight-inch-long bar of metal into, so the 8-point bar is often bent (i.e. into a V shape) to be inserted.
Time for some visual aides:
o _____ o
o _____ _____ _____ o
|_____| |_____| |_____| |_____|
To the extent of my knowledge, only surface piercings can take Mad Max bars if someone's thought of another piercing to wear one of these in, I haven't heard about it (yet!).
Pictures of piercings with 4- and 8-point bars can be seen at the Mad Max Tattoo and Piercing website, www.madmaxtattoo.com. While you're there, you can also see some of the custom titanium jewelry Samppa's designed.