Two O-rings that fit on the hatch cover. The hatch cover is not included. To install the O-Ring you must first remove the damaged O-Ring using a small tool such as a pin, knife point or small screw driver and simply stretch the new O-Ring into place in the groove. NOTE: This will not help you if you have lost your hatch cover. It is intended for scuba divers who regularly inspect their important O-rings before dives, looking for nicks or cuts. With this set of O-rings you can install one and have one spare for the next time.
If you want the entire hatch cover with an O-Ring already installed it is available elsewhere in this order page.