This visa is available to someone who has at least 1 year of experience (within the last 3 years) as either a manager or specialized knowledge worker with a foreign company that is commonly owned and controlled by or commonly owns and controls a business in the US (or will be opening a new office in the US). The foreign national must also be coming to work for the US office as either a manager (L-1A visa) or specialized knowledge worker (L-1B visa).
The L-1A visa can be held for up to 7 years total. The visa is usually granted initially for 3 years (unless a new office is involved, in which case the visa would be granted for 1 year), and extensions are granted in 2 year increments up to the 7 years maximum. The L-1B visa can be held for up to 5 years total.