Even after more than seven decades, the model and its variants remain the most popular and widely used rifles in the world because of their reliability under harsh conditions, low production cost compared to contemporary Western weapons, availability in virtually every geographic region, and ease of use. The AK has been manufactured in many countries and has seen service with armed forces as well as irregular forces and insurgencies worldwide. The model was the basis for developing many other types of individual, crew-served and specialised firearms. , "f the estimated 500 million firearms worldwide, approximately 100 million belong to the Kalashnikov family, three-quarters of which are AK-47s".