Features and Benefits:Hone engine cylinders 3-1/4" to 4-1/8" and 83mm to 105mm in diameter to produce a plateaued finish for fast ring seating and better oil retention for longer engine life;Hone life is in excess of 1000 cylinders;Requires no setup;Use variable-speed 3/8" electric hand drill and move the Flex-Hone® up and down in the cylinder until desired results are obtained;The GEARWRENCH engine cylinder flex-hones are easy to use with a variable-speed 3/8" hand drill and require no extra setup. Available in 3 sizes, the flex-hones will provide a smooth finish for cylinders from 3-1/4 to 4-1/8" in diameter. The durable 120 grit hones will provide a smooth finish in excess of 1000 engine cylinders.