XTD Flywheels are made using the highest quality, most modern materials available. All of these materials are tempered Chrome-Moly Steel which are very strong yet very lightweight. The friction surface is very special. XTD uses a high carbon, Chrome-Moly Steel. This Chrome-Moly is perfect for this use. It is incredibly durable allowing the user to use just about any clutch disc material available from Stock organic to Kevlar,Cooper Ceramic and even sintered iron.They are specifically designed to reduce weight and inertia for better engine response. Most incorpoIncludes special design features to enhance the air flow to improve the cooling of the clutch. XTD attaches the friction surface using Heat Treated aerospace nuts and bolts or 304 stainless steel rivets depending on the application. These are some of the best fasteners money can buy. We chose them because of their incredible shear strength and resistance to corrosion. All of XTD's ring gears are heat treated for durability.