I hope these are my headphones for years to come. I absolutely love them.SOUND QUALITYThe first time I put on a pair of Sennheisers, I fell in love with the sound. It is absolutely true: you do hear subtle musical passages in familiar songs that you never knew where there. I listen to a type of music I call “Melodic Rock,” for example: Jackson Browne, Marc Cohn, the Civil Wars, Brandi Carlisle, Patty Griffin, etc. These headphones, like all Sennheisers, vastly improve the listening experience.IMPORTANT BLUETOOTH INFO:- To get the full spectrum of the Sennheiser sound experience, you really need to use the supplied audio cord, and have the headphones plugged into whatever is playing the music. Bluetooth technology still isn’t at the point where it can compete with wired sound.- HOWEVER, these cans were designed to do the very best possible through Bluetooth. It’s impressive how much they can do, even without the cord. I usually listen without the cord, just because the quality is good enough to make the hassle of being wired not worth it, most of the time.- You should make sure that whatever device you are using is set to use the bluetooth “aptX HD” audio codec for streaming. Without that, you are not getting as much out these headphones as you could. Most modern phones can do that. Google it, for your phone.NOISE CANCELINGNoise canceling comes from two sources: the seal of the cups around your ears (to keep out sound physically), and then the “active” noise canceling technology. These are terrific in both categories, and I have reasonably large ears. I can walk on an extremely loud treadmill, watch TV with these plugged into it, and not notice the treadmill at all. The treadmill in question is far louder than a cruising airplane.USING WITH A TELEPHONEI have made multiple telephone calls using these, and the people at the other end say the sound quality is great. As long as the connection is normal, the sound quality is great on my end, through the Sennheisers, also. There are two important tips, though. First, make sure that the noise canceling feature is OFF when you want to use these to talk on the phone. I don’t know why, but it makes a huge difference. Second, I slide the left can slightly off my left ear when talking on the phone.ANOTHER HELPFUL TIPI learned something years ago on a cheaper pair of headphones. There are two places where noise might physically leak through: the jack for the audio cord, and the jack for the charging cord. I took some Nexcare first aid tape. It is spongy, to seal off sound, and, most importantly, can be peeled off, and re-stuck dozens of times. I colored the tape to match the head phones, and then put one small piece over each jack. Works great, for maximum noise protection. Pictures attached.BUILDAnother reviewer said “these are plastic, but they don’t feel cheap.” That’s pretty much correct, although it’s probably not plastic, but some hybrid like ABS, or something. Anyway, they are very sturdy. I’ve dropped them a few times, with no damage. I did get a hard-backed carry case for travel, however.BATTERY LIFEI usually turn these off between uses, and they turn off automatically, if they are disconnected from a Bluetooth device for long enough. For phone calls and occasional music listening, it takes me a couple of weeks to run out the battery.