Great eye-catching design, colourful. Designed as part of a series of earphones, between BMW and Sennheiser. Additional (extra) branding by Adidas.
Check out my review of the CX870 for more information as the sound signature and tuning are almost the same.
Overall, sound is great, good bass response. But strangely, the CX680 is pretty loud, much louder than the CZ870. The CX680 is also of a slightly less refined sound than the CX870.
These are waterproof sports earphones with Kevlar reinforcing on the cables!
I don't know what Sennheiser had in mind when they designed this, but the earphone is too short to use normally without the extension, and too long and heavy to use with the extension. It's only good if you're wearing an armband, but even then, it might still be a little short. In conclusion, it sucks.
Go for the CX680i if you really need a Sennheiser sports in ear, as the cable is at least of normal length lol.