PistonThis ring is for anyone that knows their way around an engine. The ring not only looks cool, but the piston actually works! When the thumbwheel is rotated around, the piston goes in and out in perfect harmonic motion. The fact that it all fits on a finger makes it that much more amazing. The ring is crafted from titanium, so water or chemicals won't hurt it. The ring shown was made in a size 10 and is about 6. 4mm wide.