M+N steel cord for reinforcing rubber product

A steel cord for rubber reinforcement, the steel cord comprising a first group of core filaments and a second group of sheath filaments being twisted with each other,

• the first group of core filaments having a number of m core filaments,
• wherein m is three or four,
• wherein the first group of core filaments collectively forms a helix,
• wherein the individual core filaments from the first group do not cross over each other, and
• wherein the core filaments are substantially parallel or have a twist pitch of more than 300 mm, the second group of sheath filaments having a number of n sheath filaments,
• wherein the second group of sheath filaments forms a flattened helix in the same direction of the helix of the core filaments, the sheath filaments having a cord twist pitch,
• wherein, at every cross-section of the steel cord, at least one interstice between two adjacent core filaments is present, and
• wherein said interstice is measured by the shortest distance L between said adjacent two core filaments, L being greater than 0 mm and smaller or equal to 0.1 mm.