Tountinna, the highest peak, does not qualify as a mountain using the usual convention whereby a mountain is defined (in Ireland and the UK) as any summit at least high, whilst the official UK government's definition of a mountain is a summit of 600 metres or higher. In addition, some definitions also include a topographical prominence requirement, typically 100 feet (30 m) or 500 feet (152 m). In practice, mountains in Scotland are frequently referred to as hills no matter what their height, as reflected in names such as the Cuillin Hills and the Torridon Hills. In Wales, the distinction is more a term of land use and appearance and has nothing to do with height. For a while, the US defined a mountain as being 1,000 feet (304.8 m) or more tall. Any similar landform lower than this height was considered a hill. However, today, the United States Geological Survey (USGS) concludes that these terms do not have technical definitions in the US. However both the Placenames Database of Ireland and the Ordnance Survey of Ireland refer to the Arra range as mountains, not hills.