If I understand correctly, all Sennheiser IEMs have a proprietary MMCX connector. Consequently (and to my never-ending chagrin and expense) if you don't get your MMCX cables from the right source, they're not going to fit securely to your Senns. These work perfectly. I demand a 2 m length and most of the sellers I reviewed on EBay don't offer a cable in that length. An L-shaped 2.5 mm plug would be preferable, but I like the cable quality and workmanship.