I had the Stealth 400 headphones for over 3 years before the weakest part of the build broke, then I switched to the 600 headphones.FYI I take full responsibility for the 400 break since i wear them before bed (surfing youtube) during my nightly routine (again for 3+ years). From a design point of view, 600 corresponds to all the checkboxes I want. see an improvement over the 400s. These include: a switch to mute the mic (biggest wish), increased structural rigidity at an adjustable point between the strap and the actual headphones, and a reduced change in the volume of the operating system's voice (think Siri, but very loud and slow ). My only complaint about the 600s is that the maximum volume is nowhere near the maximum volume of the 400s (compared side by side). That's why the product itself, not the seller, gets 4 stars instead of 5.