Horse outward similarity is an unreliable measure of relatedness. Besides the horse, there are six other species of genus "Equus" in the Equidae family. These are the ass or donkey, "Equus asinus"; the mountain zebra, "Equus zebra"; plains zebra, "Equus quagga"; Grévy's zebra, "Equus grevyi"; the kiang, "Equus kiang"; and the onager, "Equus hemionus". Horses can crossbreed with other members of their genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey). Other hybrids include the zorse,
Hyundai Equus support and a massage system. Hyundai also developed an armoured vehicle based on the limousine, with an enlarged 5.5L version of the V8 engine. On September 2009, Hyundai delivered three bulletproof limousine versions of the luxury sedan Equus to the South Korea Presidential Security Service to be used as the official state car. Hyundai designed this vehicle with a special alloy, with an automatic cooling system in case of fire as well as bulletproof windows. The first-built armoured limousine was donated to Blue House. A modified Hyundai Equus was donated to Costa Rica and is currently used as the presidential