In 1999 IRCAM was equipped with the Mauna Kea consortium L' and M' filters and a program initiated to reobserve standards through the new filter set and to establish fainter L' standards. The filters are described in "The Mauna Kea Observatories Near-Infrared Filter Set. I. Defining Optimal 1-5 Micron Bandpasses" by Simons & Tokunaga 2002 PASP 114, 169 and "The Mauna Kea Observatories Near-Infrared Filter Set. II. Specifications for a New JHKL'M' Filter Set for Infrared Astronomy" by Tokunaga et al. 2002 PASP, 114, 180. Our results appear in L' and M' standard stars for the Mauna Kea Observatories Near-Infrared (MKO-NIR) system by Leggett et al. 2003 Mon.Not.R.astr.Soc. 345, 144. The results are summarised below, where we also give links to older files giving L and M magnitudes for brighter standards. Note the older results are not on the MK system however differences between L' and M' systems are expected to be small for these spectral types (see discussion in Leggett et al. 2003).