Threader hoops made of work-hardened, lightweight aluminium, closed with a hardened aluminium spring in a rustic, weathered matte War Rig finish. These are designed to fit through tunnels in gauged piercings. The thickness is approximately 3.25 mm for the 6g or 4mm for the 4g, with the hoops themselves measuring 2" (5cm) in diameter in the larger and 1 1/4" (3.5cm) in the minis. They look heavy, but are actually very lightweight.
Named after the great inventor and showman, Nikolai Tesla. Here's a quick video
showing how to take off and put on my Tesla coil hoops.