If you are experiencing problems with breaking strings then this article may help isolate some issues.
”Strings do break from age or because of a flaw in the string but most string breakages are caused by a problem with the instrument…”
Rotosound Swing Bass 66 SM66N Roundwound Nickel 40-100 Hybrid
Rotosound Swing Bass nickel plated bass strings have a more vintage-vibe to them than the regular stainless steel swing bass strings. The slightly softer, smoother tone of the nickel plated Swing Bass strings makes them a good alternative to the punchier-sounding stainless steel.
The most popular Roundwound bass string ever. Rotosound was the first string company to produce this kind of string. Introduced in 1962 it changed the sound of the instrument instantly. The favourite string of many players including Billy Sheehan, John Paul Jones and Geddy Lee. Available in all popular gauges and scale lengths. The steel used to produce these strings is unique, combined with a highly secretive manufacturing process.