Perfect Quality. Works as expected. I used this cable to link a mellanox Connect-x 3 card with a QSFP ending (40gpbs) in my workstation to a standard SFP+ switch at 10gbps. Only the first link works (you have to leave 3 sfp+ endings hanging) but saves you from buying a QSA (QSFP to SFP+ adapter) and a SFP+ DAC cable instead.

Worked flawlessly with custom dual customization. Super fast shipping was specially pleasing. Absolutely worth it.

Good quality

Use the cable to connect from Arista DCS-7060CX-32S to Brocade ICX 7250.

the cables and it just works.

Very pleased with the quality of the 40G QSFP+ to 4 SFP+ DAC. I ordered many different lengths of DAC cables and used them extensively on Nexus 6000 and 9000 series and they all performed perfectly. Highly recommend these items which feature with great compatibility and excellent performing.

I’ve tried the breakout cables in Cisco Nexus 5000 N55-M4Q and they worked very well. These days, we are planning to purchase new equipment for our project and we will still choose FS as the first site.

Still remembered the first deal with FS. We had the equipment with 100G CFP port, and wanted to buy QSFP28 modules to connect our 100G CFP module. But we didn’t know whether it was OK. So we asked FS whether they could do the test. The technical staff kindly tested the connection of 100G CFP and QSFP28 of the same wavelength. And they sent the testing report to us. We bought the 100G QSFP28 modules, and they worked fine with our CFP module.
This time, we came again and decided to use 40G and 10G modules to make 40-10G connection. The sales knew our network environment, we planned to make the connection in the streaming room, and the devices were about 2m away from each other. So the guy recommended the DAC cable #30903. A much more cost-effective product for us.

Bought this for 10G-40G upgrade. But on the 40G side was a Cisco switch, and 10G switch was made by Juniper. The sales assured us that we could use “customized service” to solve this problem. So we got a “customized” product. We tested the DAC on our devices, the TX and RX powers were within the spec.

Our business has expanded greatly this year, we considered extending and upgrading our network in a comprehensive way at the end of this year, so it can provide a better service next year. To upgrade our existing 10G network to a 40G one, we also hoped the original ubiquiti 10G switches, connected with dell servers, can be fully used. After all, replacing all the 10G devices would be too much costly for us. The problem was we had already had 40G nic cards. We wondered if it was possible that those 40G nics can be used together with these 10G switches.
After describing our confusion, my account manager told us there were three solutions to solve it. They also confirmed our network environment and the transmission distance about the devices needed to be connected. Based on that, he also pointed out the most economical solution for us was to use 40G dac cables. Since our transmission distances were no longer than 5 meters, using transceivers together with mtp break out cables or transceivers together with optical cables and qsa adapters would both be more expensive. This was the most considerate and professional service we had ever had. Because of that, we bought their product without any hesitation.
Now, we have used their products for a while. Everything goes well just as we had expected.

I got this DAC cable to use as an uplink from my Cisco 10G switch to my Cisco 40G switch.
The cable is fully compatible and able to get my QSFP+ link up. Overall, decent cable for the price.