Historically, anaesthetic equipment manufacturers used a number of differently-sized connectors in anaesthetic breathing systems. This gave rise to the potentially dangerous possibility of mismatched taper connections and a failure to create a gas-tight breathing system capable of ventilating a patient. The British Standard 3849 of 1965 attempted to correct this problem but manufacturers' designs, in some cases, still caused problems. The problem was aggravated by a move to adopt a slightly different International Standards Organisation design. By the time that universally-interchangeable connectors were widespread twenty years later disposable breathing systems had replaced the old, heavy metal connectors.