Review on QSFPTEK 10G SFP RJ45 Module, 10Gbe Mini-GBIC SFP+ to RJ45 Module - 10GBASE-T Copper Transceiver for Ubiquiti UF-RJ45-10G, Netgear AXM765, Supermicro, Unifi - Up to 30m by Daniel Jenkins

I bought this to connect to a 2.5gb ethernet USB to manufacture adapters (RT8156 chipset). The connection speed was correct and the transfer speed was great. The reception speed only reached 600 Mbps. I even connected to a 1Gbps ethernet connection and was only able to get 600Mbps with this transceiver. All tests were performed with iperf3. I am returning this device for another brand with hopefully better support for getting 1/2.5/5GB. I tried this on two different switches with the same result. Edit - I increased the rating to 5 stars because the receive speed issue was fixed by enabling upstream rate limiting on the switch port. The switch used to spam only the 10Gbps sfp+ adapter, now it's limited by the switch. Ideally, the sfp+ module should connect to the switch at the same speed as the client device, but this is not the case.