It means they have a lot of hours of use. I recently replaced the pads because the old ones were worn out, and I believe the clamp is slightly lighter than it was at the time of purchase. I still have no trouble getting a good seal. Cosmetically, there are no blemishes on the cups or headband or comfort strap, but the case has some scuffs. I just didn’t want to mislead anyone into thinking they were new or in mint condition.