These are definitely the best strings for a rock n roll / rockabilly bass.
I'm using them on the 3/4 double bass I play in a rockabilly / rock n roll / psychobilly band I'm in.
They have a nice sound that works good with slapping (that's why they advertise them like that) and somehow seems a little easier and softer than I was expecting.
As far as the sound goes, they're good (specially having the price in mind) and as expected on a double bass, the sound is write warm, although, when slapped, they have the highs and mid highs that cone with slapping (which is good!).
They also come in a very nice box.
I personally like them quite a lot, and totally recommend it, if you are not onto spending a lot of money on a set of bass strings.