I feel that this mod vastly improves the appearance of the glass helmet, particularly on male characters. On males you can actually see through the helmet on either side of the characters head. The fit for the female helmets isn't nearly as bad, and from what I can tell, this mod only slightly narrows the top of the female helmet.
This mod is actually a combination of the meshes from Better Fitting Glass Helmet by Abakus and some esp changes that fix an issue with elven ears clipping through the side of the helmet. The ear clipping issue is present with both the vanilla meshes and the "better fitting" meshes, so this mod's fixes are valid even if the altered meshes aren't used.
Here are some comparisons. The files are named in a way which should hopefully make it clear which are vanilla and which are from this mod.