Raceworks Performance Billet Aluminium Line Separator ID 4.8mm (3/16") Black - RWF-156-05MM. Raceworks Billet Aluminium Line Separator ID 4.8mm (3/16\") - Black. Crafted from high-quality 6061-T6 billet aluminium, this line separator combines unparalleled durability with a sleek, professional look that enhances any custom vehicle build.