The impala is a medium-sized, slender antelope similar to the kob or Grant’s gazelle in build. The head-and-body length is around 130 centimetres (51 in). Males reach approximately 75–92 centimetres (30–36 in) at the shoulder, while females are 70–85 centimetres (28–33 in) tall. Males typically weigh 53–76 kilograms (117–168 lb) and females 40–53 kilograms (88–117 lb). Sexually dimorphic, females are hornless and smaller than males. Males grow slender, lyre-shaped horns 45–92 centimetres (18–36 in) long. The horns, strongly ridged and divergent, are circular in section and hollow at the base. Their arch-like structure allows interlocking of horns, which helps a male throw off his opponent during fights; horns also protect the skull from damage.