These headphones are ideal for long flights. In addition to having overall impressive noise-cancelling (-33dB across all frequencies on some tests), these headphones excel when you need to cancel out low frequencies like jet engine sounds (-45dB).
You aren’t likely to have issues using these on the go. Most active noise cancelling in-ear headphones have large control modules, while the K391NC has a fairly compact and light module. You can easily use these headphones while walking and comfortably enjoy active noise cancelling with your music.
These headphones will sound great with a practically all genres of music. The highs are slightly rolled-off, but still present a good level of detail, so these headphones are not harsh. The mids are warm, while the bass is controlled instead of boomy.
If you are a tall person, you may have a problem positioning the large active noise cancelling module. The wire connecting the module to the earpieces is quite short. This can make it a little difficult to clip the module to your belt or pocket, which can get annoying.