Emerald Changers are basically replacements of Chaos Emeralds. When activated, they turn the user into their super forms. Keep in mind that there are only six of these. Some of you may have been wondering why Sonic and the others own them. Sonic received 5 of them from a meteor shower and kept one. Naturally, he gave one to Tails and another to Knuckles. Jet was given his after saving Sonic from an oncoming truck. Shadow got his when he joined the Emerald Fighters. I hope this helps in answering questions you may have about the Emerald Changers.