A Mitutoyo accessory designed to assist in deep-hole measurement by extending the reach of a standard bore gauge by 1000mm. Note that when several extension rods are joined together there is the possibility of small errors arising from the extra joints involved. Therefore it is good practice not to connect more than 2 rods to a bore gauge at any one time. If possible use a single, longer extension rod rather than several shorter ones. The bore gauge should be used in the vertical orientation with this rod, and accuracy and satisfactory operation should be confirmed after connection.