Protect your engine from over revving with the dui rev Limiter this soft touch rev Limiter uses Sophisticated computer circuitry to drop spark one cylinder at a time, until your engine is at or below its maximum RPM. Those cylinders are then fired on the next cycle, to prevent them from loading up with fuel. The result is smooth rev limiting action that prevents backfires and possible engine damage. RPM limits are set with plug-in modules. A 6000, 7000 and 8000 RPM Module is included with the rev Limiter but other RPM limiting modules are available in separate kits. Works with All HEI and dui distributors.