This AquaTech Replacement O-Ring contains all of the user replaceable O-Rings for the AquaTech ATB Water Housings.  The O-Ring kit contains the rear main O-Ring and a Port Based Compression Seal O-Ring which is for the front of the Water Housing.

Manufactured to the precision tolerances required to hold a pressure seal on your housing and made of silicon material, it provides the means by which a watertight seal is formed.  Silicon O-rings are easy to maintain.  It is important to keep them free of dirt and sand, but O-Ring grease is not required.