The invention provides a steel cord with a construction of n1, n is the number of the steel filaments of the steel cord, the steel cord has an elongation at 2.5N-50N of less than 1.2% and a twist pitch of greater than 16 mm, each of the steel filaments has a form of helical wave with a wave length L expressed in mm and a wave height H expressed in mm when being unravelled from said steel cord, L is greater than 16 mm, each of the steel filaments has a space volume Vs satisfying that, Vs=LH.sup.2/4, and Vs>20 mm.sup.3. The invention steel cord is beneficial for the stress distribution.