15 mm x 1/2" UK manufactured compression fittings Made by BS EN ISO 9001:2008 companies, to BS 864-2:1983 or BS EN 1254:1998. They conform to both these standards apart from marking ; a fitting conforms to the standard with which it is marked. Except that sizes 4 mm and 5 mm are manufactured in the UK to BS 2051:2:1984. Compression x BSP Taper Male - Straight Adaptors.