Had those for the FitEar and didn't care for the ergonomics. Maybe it's better now since I had the first version.A couple of us use this cable with good results. YMMVhttp://m.ebay.com/itm/251510993064?nav=SEARCH
It snaps on and off on the sides. Looks like it just protects the volume knob and maybe keep the dust out. I don't see a real purpose for it. Comes off and on easily. Just be careful not to be too forceful so the knobs don't break.