Instruct: Classify the given review into positive or negative sentiment.
Query: Great value! Very durable!

So I was just looking at my order history, and it turns out I've been using this night guard for 25 months now. It comes with two and I still have the second one saved in a plastic bag for future use. It has definitely seen better days, but it continues to prevent me from grinding my teeth. Sure, some nights if I'm super-restless it'll come out, but in general it does a great job. The one thing I'm curious about is why they made it from two separate pieces of plastic (at least the version I got in 2006). It seems like they're just destined to separate, especially given that the whole purpose is to stop my teeth from grinding each other by taking the bullet itself. So the top layer is pretty much worn away by now, but as I said, the thing still does its job. If I ever need another one, I'm definitely gonna order this one again!