If you own a Seiko Samurai (SRPB49, SRPB51, SRPB53, SRPB55, SRPB99, or SRPC93), this is the caseback gasket you need for your angular two hundred metre Prospex diver. These round profile O-rings are specifically sized for the Samurai case back, and are slightly smaller than the Turtle equivalent, so make sure you've got the right one for your watch. This gasket sits in the groove on the underside of your caseback and creates a watertight seal against the case body when the back is screwed down. Over time, the rubber perishes, dries out, or gets compressed and loses its springiness, which means your watch is no longer water resistant. Replacing this gasket restores that critical seal and keeps moisture out of the movement.
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