5MLSI, Cutler Hammer, Digitrip RMS 520M trip unit or programmer, with 4 digit LCD display, programmable to any amperage requirement, 200 - 6000A, solid state electronic, LSI - Long-Time, Short-Time and Instantaneous trip functions, suitable for use with Magnum MDS, MDN, DS, DSL, DSII, DSLII insulated case circuit breakers