The Siemens SIRIUS 3RT2518-1BW40 is a Size S00 contactor with a 24 VDC coil, screw-type terminals for the main circuit, and a 45 mm width that snaps onto a standard 35 mm DIN rail per DIN EN 50022. Rated for a 24 VDC coil, it switches DC loads up to 10 A at 24 V, 2 A at 48 V or 60 V, and handles 10 A at 230 V AC — so it's suited for control transformers, small motor loads, and resistive heating elements in a panel. The S00 frame keeps the footprint tight at 57.5 mm high and 73 mm deep, leaving room for auxiliary contact blocks alongside.
The DC switching table tells you the real story: at 24 V it's good for 10 A, but at 220 V DC that drops to 0.3 A, and at 600 V DC it's only 0.1 A. That's the arc-quenching limit of a contactor this size — don't expect it to break a 600 VDC motor circuit at full current.
Side-by-side mounting is allowed with zero clearance on all sides except 6 mm sideways spacing for heat dissipation. Terminals accept solid or stranded wire: 2x 0.5 to 1.5 mm², 2x 0.75 to 2.5 mm², or 2x 4 mm² — covers most control wiring you'll run in a panel.