The invention relates to a tensioning or deflector pulley, in particular for the belt drive on an internal combustion engine, essentially comprising a plastic or steel running pulley, formed by an inner hub ring, an outer running ring and a pulley disc, connecting both rings to each other, with a radial roller bearing fixed in the hub ring of the running pulley, made up of an inner bearing ring and an outer bearing ring with a number of rolling bodies running between the bearing rings in channeled running tracks, retained at regular separations from each other by a bearing cage with a seal to both sides of the roller bodies, by means of which the cavity, formed between the bearing rings and designed as a grease reservoir, is sealed.