Essential component of the GPI mannosyltransferase 2 complex. Responsible for the transfer of the second mannose to the glycosylphosphatidylinositol during GPI precursor assembly (By similarity). Glycolipid biosynthesis; glycosylphosphatidylinositol-anchor biosynthesis. Part of the GPI mannosyltransferase 2 complex composed of gpi18 and C167.09.