mitutoyo extension rod 250mm for bore gauge extension rod length250mm / 10" extension rod diameterø12 applicable measuring range35-60mm / 1.4-2.5", 50-150mm / 2-6", 100-160mm / 4-6.5", 60-100mm / 2.4-4", 100-160mm / 4-6.4" a mitutoyo accessory designed to assist in deep-hole measurement by extending the reach of a standard bore gauge by 125mm. 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. satisfactory operation should be confirmed after connecting this rod to the gauge.