This handy little tool takes all the guesswork out of choosing the correct graphite or steel extension. Simply insert the Premium Extension Gauge into the butt end of the shaft needing an extension and match the color code with the GW4000 butt extension color. Eliminates the need for excessive sanding or build up tape to fit those larger and smaller butt diameters that club makers are constantly encountering. Note: The correct color dot is inside the golf shaft just below the next visible colored dot outside of the shaft butt.