The Schneider Electric TeSys K LP5K12017BW3 is a reversing contactor — a single device that handles forward/reverse switching for a three-phase motor without a separate mechanical interlock. It's preassembled with the reversing power busbar, so the interlock wiring is already in place. Rated 12 A in AC-3 duty up to 440 V, it controls motors up to roughly 5.5 kW at 400 V (common rule of thumb for this class). The 24 V DC coil with one normally-closed auxiliary contact suits PLC-driven panels where the control voltage is 24 VDC and the NC contact can be used for status feedback or safety chain monitoring.
AC-3 at 12 A means this contactor is rated for starting and stopping squirrel-cage motors — the worst-case current is during start-up (typically 6-8x FLA), and the contactor must handle that without welding. The 12 A figure is the motor full-load current it can switch, not the inrush. AC-4 rating (also listed) covers plugging and inching duty where the contactor opens under full locked-rotor current; that's a harder thermal cycle, so if your application involves frequent reversing under load, the AC-4 rating is the one to watch.
The 57 mm depth and 90 mm width fit a standard 4-module-wide panel footprint. Preassembled reversing busbar saves the wiring step that's a common source of errors — no risk of mis-wiring the mechanical interlock.