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They say "New layup for weight saving" and
"Standard: Each rim carries its own layup schedule documents which are followed meticulously by the layup workers. Our Engineering team creates a unique fiber orientation which amplifies the desired riding characteristics for a given rim.
Flyweight: New layup design at the nipple bed to reduce the amount of material required and reinforce the key area around the spoke holes."
I meant the difference between the flyweight and the standard versions!