This is a replacement headband for Sennheiser HD580, HD600 and HD650. The Sennheiser part number is 059570. My HD580s cracked in the middle of the headband and broke in half. I called Sennheiser to purchase a replacement part and they wanted $100 for a new one. I took measurements from the broken headband and came up with this model. Every part fits and functions as it was originally designed.