I bought these headphones on the recommendation of Stuff magazine I was not expecting them to be fantastic given the price (£9 from play) but I was totally wrong.
These are the best set of in ear headphones I have ever used.
The bass is full and thumping, the treble is not overpowering and they have a large range.
They sound great with no equalizer setting on my iPhone though any setting i do add usually takes away from the pure sound of the sennheiser headphones. The cord is long enough for personal use but is a little too short for gaming (unless you sit on top of your PC!)
The buds feel great, plus you get a choice of small medium and large which means you can tailor them to your needs. I personally do not find them uncomfortable to wear but i have friends who refuse to wear in ear headphones so ultimately it comes down to personal preference. The CX 300 II come with a few extras such as an official sennheiser carry case which matches the headphones for style and elegance plus is quite handy to have.
I was happy to see a clip included in the bundle so i can attach them to my jacket etc while out and about.
The jack is gold plated and is of decent quality and the connector feels robust allowing for a little movement of the wire.
If you like in ear headphones then these do the job perfectly at a price point under a tenner. however if you prefer over ear headphones or actual studio style headphones then i would look else where.