SFP is a type of port typically found in professional networking equipment. This is a 10G SFP+ RJ45 adapter. RJ45 is the name of the port that you plug a CAT6/ethernet cable into. This adapter allows you to plus a CAT6 cable into the SFP+ port in the ASUS RT-AX89X AX6000 router.

Gilligan, just wanted to pop back in and give a quick update on my situation. I bought the 10Gtek 30m transceiver (this one) from Amazon for $40 and IT SOLVED THE PROBLEM!! Thank you so much for the advice! I would have purchased the one you linked but it's out of stock until Feb. I'm getting transfer speeds to my 8x4tb pool (spinning hard drives) of over 400mb/s, which is great (at least, I think it is).

I really hope this helps those who are on the fence about the Mikrotik CRS305-1G-4S+IN. It was easy to setup. I just put it in SwOS mode and it basically acts like an unmanaged 10Gbps switch. This was all accomplished in my build with a 55ft run of Cat6 cable (no Cat6a or Cat7).

Thank you so much for you help!!