Sennheiser Molds For DIY Headphone cables

[grandenigma1]

You will have a hard time fitting anything much larger than 22awg.

[n_maher]

Originally Posted by Edwood

What's the largest diameter (gauge) of wires that can possibly fit these?

Just to add to what GE said, 22ga is about it and seems limited by the size of the stock strain relief. So if you had some heavier gauge wire that had a very thin coating you might get it to work, although why someone would use heavier than 22ga wire for a headphone cable is beyond me.