Kung Fu Finger Magic Golden Ring Self Defense Brass Knuckle Survival Tool. Hopefully the Kung Fu Power Self-Defense Ring is something you'll never need to use, but it's much better to be safe than sorry when it comes to your safety. The Kung Fu Power Self-Defense Ring starts off as a simple, stacked ring, but after being fanned out the device can be worn like brass knuckles to quickly break things around you or provide additional power when fighting an attacker.