Stainless Steel BSP Ball Valves are used in applications that don't require the use of sanitary grade fittings. They are also normally used in pipe applications, not tube, BSP fittings are often referred to as WOG fittings (water, oil, gas fittings).

Ball valves are durable and usually work to achieve perfect shut off even after years of disuse. They are therefore an excellent choice for shut off applications (and are often preferred to globe valves. They do not offer the fine control that may be necessary in throttling applications but are sometimes used for this purpose. (Wikipedia)

The 1 Piece Ball Valves are the lowest cost ball valve available and are used in applications where they are only opened or closed very infrequently. They are a throw away item and the seals are not replaceable.