Checkline Mountz RDA [RDA-500F] Rundown Fixture, 3/4" Drive, 500 Lb-ft / 677 Nm Capacity. Run down adapters (RDA) are designed to provide consistent and reliable torque readings when testing power driven torque control tools. RDA’s reduce the impact and irregular peaks that cause poor repeatability. Each RDA has an effective torque range and will provide repeatable torque data within that range if used correctly. The run down adapter is mounted in-line between the tool drive and transducer.