What Causes a Thin Black Line on full Custom Outfits?

If it does I can't find it, I will recheck but I thought that one has only the Alpha mesh and the Matbasetexture and no more files. That's why it bugs me because I couldn't see if they have a layer underneath or over it. I wonder how to fix it, so I can keep it in my game. I have a few more like that, too.