0.001 inch dial indicator. Check rod bolts the proper way, because sometimes torque readings may vary. Using the stretch factors supplied by rod bolt manufacturers, this stretch gauge offers a highly accurate way to measure torque pre-load. With a special, high-tension spring, this gauge remains conveniently positioned on the bolt during tightening, with adjustability for bolts up to 2.75 inches long. Simply position the stretch gauge over the length of the rod bolt before applying torque, take a reading, and record it. Then torque down to the proper torque setting, and take another reading with the stretch gauge. Calculate the difference and check the manufacturer specifications. Sold individually.