Steel core A & D (chrome wound), tungsten-wound rope core G & C. Jargar's warmest, richest, and most powerful cello strings. Direct, responsive tone with excellent projection. 4/4 size, medium gauge.  Strings should generally be changed every 6–12 months, though students usually change them less frequently. Even if strings haven't broken, they gradually lose their brilliance and responsiveness — if your instrument sounds dull or takes longer to settle in tune, it's time for a fresh set.