Windsurfing is a surface water sport that combines elements of surfing and sailing. It consists of a board usually 2 to 2.5 metres (6 ft 7 in to 8 ft 2 in) long, with displacements typically between 45 and 150 litres (9.9 and 33.0 imp gal; 12 and 40 US gal), powered by wind on a sail. The rig is connected to the board by a free-rotating universal joint and consists of a mast, boom and sail. The sail area generally ranges from 1.5 to 12 square metres (16 to 129 sq ft) depending on the conditions, Source :