Lang Tools 5223 - 4MM HEX KEY BIT WRENCH SET Used to connect and disconnect the wiring harness connection terminal to the ECM on CUMMINS engines. Consists of a fine tooth bit wrench combined with a special 2-1/4" length, 4mm six-point key (1/4" s Fits the wiring harness connection terminals on CUMMINS ISM, ISL, ISC and ISB Most advantageous on the market for working on EGR equipped ISX engines Dimensions: 4" X 10" X 0.375"