Invisible Hearing aid???

An old friend came to the barbershop the other day, it had been almost five years since I last saw him. I hooked him up with a nice haircut for old time sake. While I was cutting his hair I noticed something different about him, I didn’t have to remove his hearing aid this time. I figured that his hearing problem had been corrected since he had no trouble listening to and participating in our conversation.
A couple of weeks later he came back for another haircut. This time the shop wasn’t so busy. We reminisced about old times and he told a story about how his crazy ex girlfriend broke his hearing aid. After laughing about the story, he mentioned that his new ones are invisible. They used to be huge back in the day, now they are smaller than ear plugs. Technology has come a long way!!