Thanks, I actually meant having a single slot, ie. a single mesh for arms, torso face and legs and not separating them out into separate slots? and hence needing an atlas. is there a reason not to do this? My reason is, that as soon as i separate the arms legs etc. in blender, i can see defects in the surface that are visible in unity. The seams themselves are patched perfectly and the unified mesh looks great in unity, but where the individual pieces are together they catch the light differently, maybe have slight differences in angles on the faces adjacent to the cut lines, making them look like separate pieces (and this is visible in blender and unity). So i wondered, why cut the mesh up? why not leave the skin as one single mesh (and hence i would need to make an atlas prior to preparing the UMA)? is there any negative to doing this?