The 3RA2110-4AD18-1AP0: It ships as a pre-assembled unit containing the 3RT2018-1AP01 contactor and the 3RA1921-1DA00 link module, so you get one order code instead of three line items on the BOM.
Snaps onto 60 mm busbars — no DIN rail adapter needed
Mounting position is vertical only, with 50 mm clearance required above, 20 mm forward, 20 mm at the side, and 10 mm below — the backwards clearance is zero, meaning the back of the unit sits flush against the mounting surface.
