I DO NOT HAVE ANY IDEA HOW IT WORKS THIS THING,I THOUGHT THAT IT WILL BE A METAL NECKLACE, IS NOT! LOOKS LIKE ANY CLOTH NECKLACE,BUT THE VERY FIRST DAY WHEN I GET IT, I WORE IT, AND OH MY GOD! THIS THING IT WORKS WITH ME, I USE TO MAKE WORK OUT, IS HARD, BUT NOT CRAZY,ALSO I WORK AS CHEF, ALL THIS FACTORS GAVE ME A SHOULDER’S PAIN EVERY SINGLE DAY, EVERY SINGLE MORNING, SO I DECIDED TO BUY SOMETHING DIFFERENT, I SEARCH A LOT! LOOKING FOR PILLS, CREAMS, PAIN RELIEF, EVERY THING, THEN I SAW ONE OF THIS GUY ON EBAY, OF COURSE THE PRICE IT WAS TO HIGH,SO I TAKE A LOOK HERE AND THERE I FOUND A LOT OF PEOPLE SELLING THIS GUYS.AT THE END I FOUND THIS SELLER,AND I PLACED MY ORDER, NEXT MORNING .EARLY I’VE GOT AN EMAIL FROM THIS GUYS, MY ITEM WAS SHIPPED THAT MORNING.LESS THAN 10 HOURS! I GOT MY NECKLACE IN LIKE 2 OR 3 DAYS,DO NOT REMEMBER,BUT YES, IT WORKS, I DO NOT KNOW IF WILL WORK WITH ANOTHER PEOPLE,BUT IT WORKS VERY WELL WITH ME! GIVE THIS GUY A CHANCE,MAYBE YOU’LL LOVE IT!