Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Great product

This is a rubber, ribbed necklace. It fits great and looks great, better than expected. I've been visiting a chiropractor for the last few weeks and as I put on the necklace I noticed I didn't have to go visit the doctor this week. Mayybe mind over matter, but I'm going to give it a try. I haven't worn it to sleep yet but I'm going to try it. Been a poor sleeper all my life. Will see if it works there too. Great customer service. They sent the wrong size the first time and I called them and they called back and exchanged it, no problems. I also ordered the bracelet and they called me on the sizes for that too. Works for me.