A full range of brass compression fit x BSP female threaded straight adapters to BS EN 1254-2:1998 is available here, this includes sizes 6mm x 1/4" – 54mm x 2" NB. All of these compression fittings are BSPP parallel threaded, WRAS approved and marked for traceability, they’re often used on plumbing and heating installations with BS EN 1057 copper pipe.
Brass compression fittings are suitable for hot & cold water, compressed air, natural gas and more, they require no special tools or hot-working for installation and can be reused due to their replaceable compression olives/ferrules. These adapters are up to 25 bar (PN25) pressure rated depending on the size and have an 85°C maximum operating temperature.