While Fall Protection Products are designed to address specific fall protection hazards, they are in fact hosed upon a more comprehensive total systems approach. To be most effective, they should be applied as part of a complete safety system that is appropriate for the environment.
In other words, just because a worker is wearing a piece of equipment does not necessary mean he is adequately protected. Incompatible components are not likely to provide the levels of protection and comfort the person requires. For the most part that means you should not mix and match components from several different manufacturers; for optimum performance and safety, rely on one manufacturer.