A reinforcement strand (400) comprises a core (403) around which steel filaments (404) are twisted all with the same final lay length and direction. The steel filaments are arranged in an intermediate layer comprising N first steel filaments and an outer layer of 2N steel filaments circumferentially arranged around the intermediate layer. In the intermediate layer filaments will contact one another at a closing lay length that is determined by the number of steel filaments N in the intermediate layer, the diameter of the core and the diameter of the first steel filaments. By choosing the final lay length and direction equal to the between two and six times the closing lay length gaps will form between the intermediate layer filaments. The 2N outer layer filaments are further divided into a group of smaller (408) and a group of larger (406) diameter steel filaments.