The Mark-10 AF021 is a Preload Option, Compatible with ESM303 Motorized Tension / Compression Test Stand. It stops the crosshead and/or zeroes the traveling display at an initial preload, and it is useful in tensile, compression, spring, elongation, and other applications. Programmable as a percentage of force gauge/load cell full scale. There are three modes (1) stop, (2) stop and zero, and (3) zero without stopping. It works with series 5 and 7 gauges only and requires 09-1214 interface cable.