Indefeasible right of use (IRU) is a type of telecommunications lease permanent contractual agreement that cannot be undone, established between the owners of a communications system and a customer of that system. The word "indefeasible" means "not capable of being annulled, or voided, or undone". The customer purchases the right to use a certain amount of the capacity of the system, for a specified number of years. IRU contracts are almost always long term, commonly lasting 20 to 30 years. The communication system can be a wire cable, such as a submarine communications cable, fiber-optic cable, or satellite. An IRU owner can unconditionally and exclusively use the relevant capacity of the IRU grantor’s network for the specified time period.