The two main types of grey markets are those of imported manufactured goods that would normally be unavailable or more expensive in a certain country and unissued securities that are not yet traded in official markets. Sometimes the term dark market is used to describe secretive, unregulated (though often technically legal) trading in commodity futures, notably crude oil in 2008.[4] This can be considered a third type of "grey market" since it is legal, yet unregulated, and probably not intended or explicitly authorised by oil producers.[5]