The Siemens 3RK1908-1CA00-0BP0 is a BU (Base Unit) cover, 30 mm wide, designed for the ET 200SP motor starter system. Its job is to protect empty slots in the motor starter rack from dust, debris, and accidental contact — a standard practice to maintain IP2x finger protection and keep the panel clean between populated modules. It snaps onto the base unit without tools (pluggable on BaseUnit) and can be mounted vertically, horizontally, or flat, giving panel builders flexibility in tight enclosures.
That covers most industrial enclosures, including unheated warehouses and shipping. Pollution degree 2 (normally non-conductive, occasional condensation) is the standard for control cabinets. Vibration resistance is specified at 15 mm amplitude to 6 Hz, then 2 g to 500 Hz; shock resistance at 6 g for 11 ms. These figures mean the cover stays seated under the vibration typical of motor starters mounted on machine frames or conveyor sections — no risk of rattling loose. Dimensions are 30 mm wide, 60 mm deep, 135 mm tall — a compact footprint that matches the 30 mm base unit slot pitch of the ET 200SP system, so it fills the gap without protruding into wiring channels.