Hone engine cylinders 3-1/4" to 4-1/8" (83mm to 105mm) in diameter. Flex-Hones produce a plateaued finish with a perfect cross-hatch for fast ring seating and better oil retention for longer engine life. Hone life is in excess of 1000 cylinders. No set-up is required. Use variable speed 3/8" electric hand drill. Hone move the Flex-Hone up and down in cylinder until desired results are obtained.