The lights that fit best in the side pocket of a LM sheath are 1 AAA lights. The Leatherman S3 is CR123A powered and would be too fat to fit. You may get it to fit by stretching the elastic, but that will make deployment and replacement of both the light and tool awkward.I would suggest an ITP A3 or Fenix LD01 light. If you are not familiar with modern lights, you will be surprised by the output these 2 are capable of. If these 2 are not within your budget, check out the Fenix E01.