Olympus PT-058 O-Ring
It may look simple at first glance. However, the Olympus POL-058 O-Ring for the PT-058 is very important because it specifically prevents water from entering the underwater camera housing. Therefore, the success of your underwater photography rests in this replacement O-ring material which is made of elastomeric rubber for flexibility and resilience especially against increased water pressure. This item perfectly fits the designated O-ring groove in the underwater case and it must only be used with a compatible O-ring grease.