The regular half jacket lenses have a flatter, straight side on the bottom and outside edge. The half jacket XLJ lenses have a concave, more curved bottom to them. The same goes for the outside edge of the lens for the XLJs. They have a curve in them toward the bottom while the regular half jacket lenses don't.EDIT: The XLJs have this funky extra bump on the outside lower edge. The regular Half Jackets look much cooler, the aesthetics are much better.