This model features an inline microphone with a play/pause button that doubles as an answer/end button when making cell phone calls. There's no volume control on the button and Spark says the microphone isn't compatible with all smartphones (it works with the iPhone but is more miss than hit with Android models). My quibble with that inline mic button is that it seems cheaply made and could fall apart over time. Also, it has a rectangular design and the edges are a little bit sharp; the button ended up snagging on my clothing from time to time, which was mildly irritating. It's not a huge deal but Id America should have gone with a design that rounded off the corners.
One of concern: I can't vouch for just how durable these earphones are. The cords are fairly thin and I don't know how well the Spark would hold up if you accidentally yanked or snagged that cord. I didn't have a problem in the two weeks or so that I've used them, but I was careful to put them in their case when not in use.