The Hoke Gyrolok instrumentation fitting Safety Changer System provides a way to re-use existing fittings and valves by fitting them with new Gyrolok nuts and ferrules. The system comprises nut and ferrule sets supplied on rods correctly pre-oriented, ensuring proper ferrule alignment and eliminating the need to handle ferrules. This is particularly useful on awkward applications and also eliminates the problem of lost nuts and ferrules. Colour-coding of individual packages to differentiate metric and Imperial sizes and component materials further ensures safety. Both nut and ferrule sets and ferrule-only sets are offered, the former including five sets of nuts, front ferrules and rear ferrules, and the latter having ten pairs of ferrules. In use the changer end is simply inserted into the fitting body, the nut is lightly threaded onto the body and the rod is extracted from the nut. There is no need to ever loosen the fitting nut to relieve or bleed system pressure, as bleed fittings are specifically designed to perform this function.