None.

comfort, sound, overall quality of the product

The earphones are made to "enter" in the ear canal and it hurts like hell.
The sound changes depeding of the angle of you neck (up/down); less bass when you look up, more bass when you look down

After 3 months, the left speaker stopped working for no reason. The wires were still welded to the speaker but it stopped working anyway. Of course, the guarantee has probably worn out after 90 days.

Customer Service

Don't care, they're going to the trash.