StarTech.com MSA Uncoded Compatible 1m 40G QSFP+ to 4x SFP+ Direct Attach Breakout Cable Twinax - 40GbE QSFP+ to 4x SFP+ Copper DAC 40 Gbps Low Power Passive Transceiver Module DAC

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This is one of those “just works” breakout DAC cables—40G QSFP+ on one end turning into four SFP+ connections on the other—so if you’ve already got a switch/server with the right QSFP+ breakout capability, it can be genuinely good value. For £32.99 ex-VAT, you’re paying reasonable money for a tidy, low-power copper link that typically saves both cabling mess and setup hassle versus optics (and you avoid buying anything more expensive just to get traffic flowing). In real deployments, these are most useful for patching between systems in the same rack/row where you don’t need reach, and where your gear supports the breakout mode.

I’d only buy it if you’re confident about compatibility—specifically that your switch/backplane actually supports “QSFP+ to 4x SFP+” breakout and that it will accept passive DACs with that polarity/format. If your hardware doesn’t support that specific breakout behaviour (or if you’re expecting long reach), it’s not the right tool and you’ll waste time troubleshooting. Also, because it’s passive, it’s not the best choice if you’re trying to cover awkward routing, high noise environments, or anything beyond very short intra-rack use—otherwise you’ll be paying for the cable and still fighting link issues. Bottom line: buy it for short, supported breakout use; don’t buy it as a universal “will probably work” workaround.