A back up display for your Poseidon CCR will add redundancy and therefore safety to dive. This Bus Block cable has two female connectors and one male connector so you can run an extra display (either an M28 or a Paddle) with your SE7EN. There is no denying that there are advantages to using two different display systems.
(2 female Connections, 1 male)
This cable has two male connections and one female. Do not use this if you are looking to run two displays with your SE7EN.
(2 male Connections, 1 female)