The terminal block case of the RK series has a high degree of protection of IP 54 to IP 66. The basic equipment includes IP 54 mounting connections and one and only mounting rail of 35 x 7.5 mm for individual placement. It has wall-mounting options in the box bottom (alterantively under the lid screws) and metric formative influence (eruption openings). No subsequent drilling or cutting - just open the holes with a screwdriver and install the provided IP 54 mounting connections The cover is made of durable polystyrene and can be serially sealed. To achieve a higher degree of protection (up to IP 66), it replaces the mounts in place of the cable fittings. The casing material is halogen free and has the UL "Yellow Card".