We order CSF-1 from Cellular Products (800-274-5487) which they now refer to as M-CSF, for macrophage colony stimulating factor. GM is granulocyte-macrophage, and G is granulocyte, and all three are different growth factors, M-CSF being the ligand for c-fms. Sue Jeffrey sjeffrey at mskcc.org What do I know, I'm only a tech!