An element for a drill string includes at least one zone bearing on a wall of the drilled hole, the bearing zone including at least one bearing section with an external diameter greater than the diameter of the other portions of the element, and two activation zones substantially adjacent to the bearing zone and disposed upstream and downstream of the bearing zone. The activation zones include a plurality of grooves with a generally helical shape about the axis of the element. The bearing zone includes two guide sections in a shape of a convex rounded body of revolution, disposed upstream and downstream of the bearing section in a manner adjacent to the bearing section, and tangential to the bearing section and to the activation zones.