Sulfur hexafluoride, abbreviated as SF6, is a nonpolar molecule. SF6 has an octahedral molecular geometry, which means that the sulfur molecule has six fluorine atoms surrounding it. While each individual bond is polar, there is no net effect, meaning that the molecule is nonpolar.
According to VSEPR theory, the fluorine molecules position themselves as far away from each other as possible. Because there are six fluorine atoms, this means that each atom is 90 degrees from its neighbors. This further means that each fluorine atom is directly opposite from another fluorine atom. The polarity of each individual bond is therefore cancelled, leaving a nonpolar molecule.