HMX-NET Carbon Fiber While we already use the proven HMF composite fiber on all our composite high-end bike models, we have improved upon conventional HMF material. This new fiber, which is produced exclusively for Scott, offers 20% more stiffness and is employed on all the areas that need additional rigidity. This new material also allows us to reduce weight and improve riding characteristics. NET stands for Naked External Tube set; the frame sheds its exterior cosmetic layer, which saves even more weight. Found on the Scott Spark, Scale, Genius and Addict high end bikes.