Mannosyltransferase involved in outer chain elongation of asparagine-linked oligosaccharides of the type Man(9)GlcNAc(2). Adds the first alpha-1,6-mannose to the Man(8)GlcNAc(2) and Man(9)GlcNAc(2), but not Man(5)GlcNAc(2), endoplasmic reticulum intermediates. Represents the first enzymatic event required for synthesis of outer chain mannose linkages on yeast secretory proteins. Has also the potential to transfer a second alpha-1,6-mannose to the Man(8)GlcNAc(2) core oligosaccharide. Transfers an alpha-D-mannosyl residue from GDP-mannose into lipid-linked oligosaccharide, forming an alpha-(1->6)-D-mannosyl-D-mannose linkage. Optimum pH is 7.5. Is recycled between the trans-Golgi network and a late compartment of the endoplasmic reticulum. Expression is regulated by SKN7, SLN1, and CDC4. The conserved DXD motif is involved in enzyme activity. Glycosylated. Stops growing at the early stage of bud formation and rapidly loses viability at the non-permissive temperature. Exhibits a defect in the initiation of the mannose outer chain. Leads to accumulation of free forms of oligosaccharides (fOSs). Present with 9490 molecules/cell in log phase SD medium. Belongs to the glycosyltransferase 32 family.