Long time user of Sennheiser gear at home and in studio. Like a few others I've seen here I've not found these to be up to their usual standards.
The location of the battery consistently puts a drag on the earbud likely pulling it out of your ear unless a very tight fit. Since I got these for use when walking or running this is a distinct problem.
Some have suggested this is due to poor quality ear bud ends but I've substituted the ends from my in-ear stage monitors (also Sennheiser) and the problem persists.
Sound wise they are fine, typical of all of their entry-level products.
So great if you want to wear them while working on a computer, not so good in my experience when moving around a lot.