Marine grade aluminum. Extruded body with die-cast end caps. Housing, with end caps, post assembly TGIC polyester powder coat finished 5-step pre-treatment. Each linear run of luminaires consists of one Beginning of Run Luminaire (B), one or multiple Middle Luminaire(s) (M), and one End of Run Luminaire (E). Specify and/or order systems per linear run (i.e. (1)B48, (5)M48, (1)E48). NOTE: Contact factory for custom lengths. See Dimensional Data for raceway. See Options for second raceway.