• The GBD Series Flex-Hone tools are designed for bore diameters from 3" thru 8" in a twisted-in-wire construction. 3 thru 4-1/2" diameter tools are 13 -1/2" OAL. 5" thru 8" diameter tools are 17-1/2" OAL. Heavy-duty Flex-Hones are commonly used for block cylinders or liners, stationary diesel, oil and gas pipes, marine engine and may other applications. The heavy duty tool is recommended for large diameter or high production applications. Additional abrasive types and grits are available.