Cobra is a large and powerful snake, averaging 3 to 4 meters (9.8 to 13 ft) in length and typically weighing about 6 kilograms (13 lb). The longest known specimen was kept captive at the London Zoo, and grew to around 18.5 to 18.8 feet (5.6 to 5.7 m) before being euthanized upon the outbreak of World War II. The heaviest wild specimen was caught at Royal Island Club in Singapore in 1951 which weighed 12 kilograms (26 lb) and measured 4.8 meters (16 ft), though an even heavier captive specimen was kept at New York Zoological Park and was measured as 12.7 kilograms (28 lb) at 4.4 meters (14 ft) long. They can be distinguished from other cobras by size and hood marks. King cobras are generally larger than other cobras, and the stripe on the neck is like the symbol "^" instead of a double or single eye(s) shape that may be seen in most of the other Asian cobras. A foolproof method of identification is if on the head, clearly visible, is the presence of a pair of large scales known as occipitals, at the back of the top of the head.