Hot-swap power supply: replace the CCR2004 or CRS504power supply without having to turn off or even restart the router.
CCR2004-16G-2S+ and CRS504-4XQ-IN units come with two hot-swap dual redundant power supplies.
If one of them goes out of order at some point, the other one will take over.
Then you can use this kit to replace the old power supply.