The GB Series Flex-Hone tools are designed for bore diameters from 3-1/4″ thru 4-5/8″ and are 13 -1/2″ OAL. These standard duty Flex-Hones tools are commonly used to finish and deglaze block cylinders or liners and represent a tremendous value on a cost per cylinder basis. Additional abrasive types and grits are available.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.The Heavy Duty GBD Series Flex-Hone tools are designed for bore diameters from 8″ thru 18″ and are constructed using an aluminum sleeve over a lightweight wood core. All tools feature a steel hex drive shaft that is 34″ OAL. Additional abrasive types and grits are available.