If you take your engine repairs seriously, you're going to want a set of these. Flex-hones are used to lightly surface the bore of your cylinder, creating a cross hatch of scratches that helps your rings seat tightly to increase compression. They also smooth over imperfections around intake and exhaust ports. This type is 240 grit aluminum oxide (AO), recommended for cylinder coatings such as chrome and Nikasil. We also offer the more industrial 320 grit silicon carbide (SC) which works on all surfaces including cast iron cylinders. Honing is done by attaching a well oiled flex hone to a hand held drill (at 600-800 RPM) and oscillating the hone up and down 8 to 10 strokes for approximately 15-20 seconds. Hones are slightly larger than bore size.