The first internally installed mass damper for mountain bikes made of 97% pure tungsten The TMD reduces vibrations and fatigue in a compact design Aluminum and steel, tapered and 1 1/8” steerers, single and dual crown, oval or cylindrical are all compatible(steerer length 0f 190mm+ required) IGUS bushings allow the mass to move freely between the 2 springs and are self lubricating Three die spring options are included and calibrated to carefully chosen frequencies(bluelight, yellowmedium and redheavy) 420g