A device for a plumbing installation, the device, for example, may be a valve, such as valve (1), or a fluid flow meter (6), and has a casing (10) that is hydraulically formed from metal tubing so as to have a wall surrounding a void interior. The casing (10) is provided with one or more formations, such as shoulders (64) and (65) and at least one inlet opening (14) and at least one outlet opening (18). A cartridge (12) is at least partly located in the void interior of the casing (10). The cartridge (12) has at least two openings, being a first opening (20) and a second opening (22). Seals (46), (48) and (50) are provided between the casing (10) and the cartridge (12). The cartridge (12) is accommodated in the casing (10) by the one or more formations of the casing (10). The cartridge (12) is provided with the operational components of the device (1). The inlet opening (14) of the casing (10) and the first opening (20) of the cartridge (12) are in fluid communication. Similarly, the second opening (22), of the cartridge (12) and the outlet opening (18) of the casing (10) are in fluid communication. A fluid flow path is thereby created through the device (1) from the inlet opening (14) of the casing (10), through the cartridge (12), to the outlet opening (18) of the casing (10).