It39s super light deadly silent and delivers an undeniable performance advantage the nine cogs in the cog cluster are machined from a single block of high grade tool steel increasing stiffness while weighing even less than a titanium cassette between each cog is a stealthring elastomer to reduce vibration and noise cutouts on the rear cog further reduce weight and add stiffness it39s the final piece in the drivetrain puzzle paired with the new sram red rear derailleur delivers ult