None.

Perfect replacement for my HD 598 Cs cable. These were originally purchased September of 2019 and I was starting to have the sound cut out on my headphones occasionally when I moved my head the wrong way. Over the past year of working from home I have to come to appreciate these headphones having a microphone so much, so I'm very glad to find an exact replacement. I'm surprised to see so many negative reviews. The cable is a perfect replacement and the free shipping got it here very quickly. I could spend $150-250 on a replacement set of headphones, but $35 to get another 1-2 years of life out of these headphones is not a bad deal to me.

There's no reason this needs to be so expensive. $45 usd for a cable is an insult to your customers. Sennheiser has sadly decided to cash in on their name.