Century Link DSL client. I replaced the main green phone wire that they get with the initial install with this shielded wire. I work in industrial electronics and shielded cable isn't always necessary, but it's not a bad idea if you have a tangled mess of cables next to a DSL modem. Add EMI and RFI power filters to the performance of your DSL modems, along with shielded CAT5/6 cables for all modem output connections, and you have the best possible conditions to boost your DSL signal in your home. Unfortunately, DSL can be a bit unstable, so I recommend taking every step to improve your signal quality.