Cables including a plurality of twisted pairs of insulated conductors, a separator disposed among the plurality of twisted pairs so as to physically separate a first twisted pair from a second twisted pair, and a jacket surrounding the plurality of twisted pairs and the separator. The jacket may include a plurality of protrusions extending away from an inner circumferential surface of the jacket toward a center of the cable. The plurality of protrusions are configured so as to hold the plurality of twisted pairs away from the inner circumferential surface of the jacket, and may provide an air gap between the plurality of twisted pairs of insulated conductors and the inner circumferential surface of the jacket. In one example, a boundary of the air gap adjacent the inner circumferential surface of the jacket is arc shaped.