The strings are nickel-coated steel, and they sound quite good and mellow when they are new.
However, the quality of the latest production is questionable. The set comes with an extra high-E string, and it was needed straight away. The high-E string installed first broke during the procedure of intonating the guitar, and it was not due to the bridge, nut or tuning machine - the string broke in the middle, somewhere around the forth fret.
Also, the strings corrode quite heavily in comparison to some other I have used.
When I used this strings previously, over a year ago, they used to be of a better quality, so it may be that I was unlucky just with the latest set.