What the ratings mean for fit
The Siemens SENTRON 5SL1201-7MB is a 2-pole miniature circuit breaker rated 1 A with a C-curve tripping characteristic. The C-curve means it trips at 5 to 10 times rated current — designed for moderate inrush loads like small motors, transformers, or lighting circuits where the startup surge exceeds a B-curve but doesn't need the D-curve's wider window. The 3 kA breaking capacity per IEC 60947-2 tells you it can safely interrupt a fault up to 3 kA at 230/400 V AC without welding contacts or cascading failure upstream. That's enough for most residential and light commercial sub-distribution boards; if your panel's prospective short-circuit current (PSCC) exceeds 3 kA, step up to the 10 kA variant in the same SENTRON family. At 36 mm wide (2 modular units), this breaker occupies two standard DIN-rail slots. Mounting position is any, so it fits vertical or horizontal busbars without derating. Depth of 76 mm and installation depth of 70 mm mean it clears most standard enclosure gland plates — check your back panel clearance if you're retrofitting into a shallow box. IP20 with connected conductors is the usual for panel-mounted MCBs; no touch-protection feature on this variant, so it's intended for enclosed distribution boards, not live-front exposed mounting.
Panel integration notes
Snap-on mounting to 35 mm DIN rail per EN 60715. The 2-module width (36 mm) means it pairs neatly with a 1-module auxiliary contact or shunt trip if you need alarm signaling. Sealable design (yes) allows the installer to lock the toggle position with a seal wire — useful for utility metering or tamper-proof circuits. Halogen-free and silicon-free construction matters if this breaker lives in a clean-room or corrosive environment where outgassing could contaminate contacts or optics.