Chromesteel on steel core.
1 out of 1 found the following review helpful
Pros: Immediate sound, soft but bright and punchy. (I had Pirastro Flexocore and Originals before and they were too tight and edgy. Feel slightly thinner under the fingers I play a mid-C.19th English bass, flat back.
Cons: I feel I need a stark rather than medium on this string. It's a fraction slower to speak.