The Customs Convention on Containers is a United Nations and International Maritime Organization treaty whereby states agree to allow intermodal containers to be temporarily brought into their states duty- and tax-free. The Convention allows for shipping containers to be brought from a ratifying state into a ratifying state duty- and tax-free for a period of three months. The Convention was somewhat superseded in 1990 by the Istanbul Convention, which combines in one single instrument the various conventions on the temporary admission of specific goods.