"Amazing sound quality, durability is hit and miss though"
Mr. P. Thorne
These are probably the best in-ear headphones I've ever owned, at least in terms of sound quality and comfort. Can easily wear them for hours and not feel any discomfort. The one thing I dislike about them is their reliability. I think I'm on my third pair since buying my first ones in 2014. They tend to last around 18 months, and then one of the headphones will just stop emitting any sound.
The good thing is there's a 2 year warranty on them, so as long as you send them to Sennheiser within the warranty period, then they'll honor their guarantee and fix them or replace them for you. So in summary, definitely worth buying for the sound quality, but just be ready for them to possibly stop working a year or two down the line.