Your retainer is made by state-of-the-art computerized equipment. This assures the product will fit perfectly according to the impression you send us. As a result, over 98% of our retainers fit perfectly. However, if for some reason your retainer does NOT fit properly, don’t panic. There are two possibilities. First, it is common for a new retainer to feel tight when you first receive it. This tightness is caused by slight movement of your teeth that occurs between the time you take your impression and the time you receive your new retainer. Give it a couple of days and your teeth will realign to the shape of the retainer making it fit comfortably. The second possibility, is that something went wrong while taking the impression. If we don’t have an adequate impression of your teeth, the result is a retainer that will not fit properly. In this case, it may be necessary to take a new impression. This possibility is why we urge getting approval on your self taken impression before sending it back. Once you take a new impression, please send it back with the retainer that didn’t fit, along with the old impression. We’ll then make a new retainer from the new impression and promptly ship it back to you.  Lastly, don't stress, you're eligible for a free replacement, for any defective product within 60-days of receipt.