erg Magnetic Necklace 42cm Red Used a few times after purchase. While there's no noticeable wear and tear, it has been used a few times, so please purchase if you understand that it is a used item. From the manufacturer: erg is a body care accessory that, by simply wearing it, balances the body and activates the inherent potential power and recovery ability that humans possess. Inside erg, special natural minerals are sealed in powder form, and this erg power emits "elementary particle super-vibration," which is the technological core of an astonishing physical sensation. The brand "erg" is loved and supported by top professionals in baseball, soccer, golf, tennis, skiing, snowboarding, road cycling, etc. Use it to improve core strength, speed, prevent falls, and reduce fatigue.