Aluminium wound on natural gut.
2 out of 3 found the following review helpful
Pros: wonderful full rich sound with great dynamic range and resonance, whilst still being very quick and responsive. Strong perfomance in upper register well suited to tonal characteristics of old cellos
Cons: not the easiest string to play and tends to need regular replacing
Other: well worth the extra effort and skill needed to make full use of it's capabilities - needs strong fingers and precise bow control to obtain the best tone