Surely such light units must be rather flimsy?

Not at all. After extensive R&D into all types of material from Carbon fibre, Aluminium, Glass fibre, Plastics, GRP Resins etc, it was eventually found that the material which gave the most rigid structure that could also take localised 'knocks' was a high carbon steel alloy. With an extremely thin wall this type of steel provides excellent stiffness and rigidity, absorbs vibration beautifully (unlike aluminium tube) and still remains light.

During R&D experiments a typical aluminium cage we produced for comparison which had to provide the same strength had to have such a large wall thickness that when measured the steel alloy cage was 3.5Kg and the aluminium unit was 5Kg. So again watch the video and ask yourself if any other manufacturer has a design that can do the same.

As with all engineering, it's all down to R&D and finding the right material for the job!