The MikroTik G1040A-60WF is a 12v 5a 60w Hot-Swap Power Supply for the CCR2004-16G-2S+, CRS510-8XS-2XQ-IN+ or CRS504-4XQ-IN units that 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 the G1040A-60WF to replace the old power supply without having to restart the router!