Product image from current catalog dataProduct overview
Bosch GMS120-27 Wall Scanner: What to Know
Bosch made several wall scanners with very similar names, and this is exactly the kind of model confusion worth flagging plainly: the original GMS120 (9V battery, illuminated LCD) has been discontinued, and Bosch's own current product catalog lists the GMS120-27 as its direct successor — third-party retailers that still list a plain "GMS120" are typically selling old stock or mislabeling the newer model. The GMS120-27 keeps the same core concept — wood stud, metal, and AC wiring detection through drywall, concrete, or plaster and lath — but updates the power system to 2 AA batteries or an optional 3.7V Li-ion pack, and adds an IP54 dust/water-resistance rating with a shock-absorbing rubber housing aimed at jobsite use rather than occasional home use.
Detection is presented through a color-coded illuminated marking ring rather than a numeric readout: green indicates no object, amber indicates an object is near, and red indicates the center of a detected object, with the ring switching to red for a detected live wire in AC mode. Bosch's published specs put metal detection depth in the range of roughly 4 inches for steel and up to about 4.75 inches for copper-type non-ferrous metal, and live-wire detection up to roughly 2 inches deep — though Bosch's spec sheet doesn't always clearly separate ferrous vs. non-ferrous figures across every retailer listing, so treat the exact depth numbers as approximate rather than a guaranteed cutoff on any given wall.
The AC-detection caveat here is one of the more specific and useful ones we found across this lineup: independent hands-on guidance on using this scanner family notes that the GMS 120 series detects the electric field around a live wire, not the wire's metal itself, so a wire inside a metal conduit or otherwise properly shielded can fail to trigger the live-wire warning even though voltage is present. The practical workaround suggested is to cross-reference a live-wire scan with Metal mode, so a detected metal object with no accompanying live-wire signal doesn't get treated as automatically safe.
Key Listed Features
Current replacement model for the discontinued Bosch GMS120, per Bosch's own product catalog
Wood stud, metal, and AC live-wire detection modes with a color-coded (green/amber/red) marking ring
IP54-rated, shock-absorbing housing built for jobsite use
Runs on 2 AA batteries or an optional 3.7V Li-ion battery pack (sold separately)
