The FF UL suffix indicates a fixed front-connection design listed to UL standards — the same breaker that goes into a UL 489 panelboard or switchboard lineup. Rated 400 A continuous, it handles feeder and large motor branch protection in commercial and industrial distribution.
The 400 A continuous rating governs the conductor sizing and the upstream feeder breaker coordination — this is the frame rating, not the trip setting. The TMG unit's adjustable thermal pickup (400–2000 A) lets you dial the long-time and short-time protection to match the load without swapping the breaker body. Three-pole construction suits three-phase 480Y/277 V or 600 V delta systems common in North American panelboards. The FF (fixed front-connection) terminals accept standard bus bar or cable lug connections; plan for a fixed-mount footprint in the switchboard, not a plug-in cradle.