Dimension Steerer Extender adds 2 to 3-1/4" height to steerer. Extender clamps to steerer; stem clamps to extender. Adds 2 to 3-1/4" height to threadless steerer. Includes top cap and long bolt. 40mm of threadless steerer is required for proper installation. Do not stack steerer extenders; no more than one steerer extender recommended per bike. WARNING: Dimension Steerer Extender is not recommended for use on forks with carbon fiber steerers