The Siemens SENTRON 5SL6104-6CC is a 1-pole miniature circuit breaker with a B tripping characteristic, rated 4 A at 230/400 V AC. The 18 mm width (one modular unit) snaps onto a DIN rail — that's another SKU that fits the same bin as any other 1P SENTRON 5SL.
At 4 A it protects a branch circuit drawing up to about 920 VA on a 230 V line. The 1-pole form factor with no neutral switching means it interrupts only the phase conductor — the neutral passes through or is bussed separately. Rated for 50 Hz AC only, with a maximum operating voltage of 440 V in multi-phase configurations and 250 V single-phase. The DC rating tops out at 72 V, so it's not a primary choice for DC battery banks or solar strings above that voltage.
Touch protection is built in (fingertip-safe terminals with connected conductors). Sealable — the cover can be locked or tagged for isolation procedures. Halogen-free and silicon-free construction, so it's safe for use in clean-room or sensitive electronic environments where outgassing matters.