A tension-leg platform (TLP) or extended tension leg platform (ETLP) is a vertically moored floating structure normally used for the offshore production of oil or gas, and is particularly suited for water depths greater than 300 metres (about 1000 ft) and less than 1500 metres (about 4900 ft). Use of tension-leg platforms has also been proposed for wind turbines. The platform is permanently moored by means of tethers or tendons grouped at each of the structure's corners.