Scraper action with floating tungsten carbide cutter. Rollers ensure easy turning. Removes ridges from all engines (including short stroke and canted types) with 2-11/16" to 5-5/16" (68.3 mm through 134.9 mm) cylinder bores. Accurately centered tool won't chatter, over-cut or damage out-of-round cylinders. Reversible. Replacement cutter blades available.