A steel cord (50) comprises a core layer and an outer layer. The core layer comprises a number of first steel filaments (10) and the outer layer comprises a number of second steel filaments (20). The outer layer is helically twisted around the core layer. The first steel filaments have a twisting pitch greater than 310 mm. At least one of the first steel filaments (10) is wavy preformed in one plane. At least one of the second steel filaments (20) is polygonally preformed.