A device for brain stimulation includes a lead having a longitudinal surface, a proximal end, a distal end and a lead body. Central and peripheral sectors are selected in an individual plane in the k-space and optionally an intermediate sector between the peripheral and central sectors is also selected. The ring is more flexible in bending about radially extending axes than about the central axis. The low-surface area, high-structure carbon black may be characterized as having a nitrogen surface area of between 15 m2g and 25 m2g and a COAN of between 65 ml100 g and 85 ml100 g.