X-Frame Frameless Frameless.X-Frame continues to be one of the most popular models. Its frameless structure makes it an unusual two-lens in that is it actually a single-lens. If this feature is further enhanced by a wide field of vision and the buckle on the skirt, X-Frame becomes and extremely practical and ideal as a back-up mask. Frame: silicone Skirt: liquid silicone Strap: silicone Lenses: single-lens in tempered glass Packaging: rigid transparent box included