Effective Spring 2016, to improve the sealing performance and O-ring life span in Shearwater NERD and Petrel2 devices (including DiveCAN controllers), the battery compartment O-ring gland design has been changed from a crushed gland to a radial gland. The cases manufactured prior to Spring 2016 use the older crushed gland design with a black O-ring. The cases manufactured from Spring 2017 on use the newer radial gland with a blue O-ring. The cases which take the new cap will be engraved RC under the strap. Select the correct type of O-ring from the drop-down menu above. The new radial gland caps can NOT be installed on older computer cases, i.e. those manufactured prior to Spring 2016. Identification of the old crushed gland cap vs the new radial gland cap can also be made by observing the differences in the table image above.

Just to be clear, if you use the wrong cap, your dive computer will flood and it will not be covered by any warranty. Battery caps have no need for periodic replacement, you should only need a battery cap if you lose yours.