The LA9FJ4G4G is a mechanical interlock from the Schneider TeSys F range, designed to prevent simultaneous closure of two contactors in a reversing or star-delta configuration. It mounts vertically between three contactors — bottom and middle positions accept LC1F185 through LC1F225 3P or 4P (or the CR1F185 equivalent), and the top position accepts LC1F400 2P, 3P, or 4P (or CR1F400).
What the interlocking means for fit
Mechanical interlocking ties the contactor armatures together so only one can close at a time — critical for preventing phase-to-phase shorts in reversing motor starters or for ensuring the main and bypass contactors in a soft-starter cabinet don't overlap. The LA9FJ4G4G handles three contactors in a vertical stack, which is a specific footprint: bottom and middle units are the smaller F185–F225 frame, top unit is the larger F400 frame. If your panel layout uses a different frame mix or horizontal mounting, this part won't fit.