Pelican 1773 O-ring replacement is a quality O-ring replacement. If you should need a replacement O Ring for your case here is what you need. Each Pelican case comes with an O-Ring in the lid to seal out any water, dust or debris. Over timethe O-Ring may deteriorate and need replacing. It maintains a watertight, moisture and dust proof seal. Having a spare on hand is important and they are easy to install