Nylon strings are great for old school jazz bass tone as well as Rockabilly slap technique. If you don't need to use a bow, you should definitely try these strings. We are huge fans of this set and we intall them a lot on customer's upright basses with great results.
These Rotosound sound great for both styles as well as Folk, Bluegrass, etc.
G and D strings are Nylon. A and E strings are monel flatwound on nylon.
The feel is just great due to the low tension so these are also great for long sessions.
If you play Rockabilly these strings feel and sound perfet for slapping (close to gut strings, actually) but the notes have more substance to them and sustain is also longer than on gut or plastic strings so you can perfectly use them for Jazz.
They take a while to stretch and hold their tuning but not as much as gut strings. They last longert than gut too.
Not suitable for arco playing
Rotosound RS4000 Double Bass Nylon