The outer sides of the device contain the adjustment slider for the bite pad. It has relatively rough edges. I wake up with an irritated swollen spot inside each cheek where those edges rubbed against me. Other than that issue the product works great. It stays in place for me well. I don't have a grinding problem but a clenching and chomping problem, so that might be the difference. I will try it one more night. This will be the third. Then I will try to get a refund if it continues. I'm not optimistic. My cheek is already feeling the leftover soreness from just putting it in.