The Siemens 3RG42107AG00 is a proximity detection switch with a sensing distance of 0.8 mm, part of the Limit and Proximity Switches category. It's used for non-contact detection of metal objects in automation lines, conveyors, or machine tools.
Key rating — what the 0.8 mm means for fit
The 0.8 mm sensing distance is the maximum range for a standard ferrous target. For non-ferrous metals, the effective range drops.