I recently installed the FOCMKEAS Recessed Wired Security Window Door Contact Sensors in my home, and I must say, they've exceeded my expectations. The compact size (19*25mm) makes them discreet and easy to install without being obtrusive.

The build quality is impressive for the price. The flame-retardant ABS shell feels sturdy, and after a few weeks of use, there's no sign of wear or deformation. I particularly appreciate the 260mm cable length - it gave me enough flexibility during installation without leaving excess wires dangling.

These NC (Normally Closed) sensors work exactly as described. When testing them, I could clearly see the circuit completing when the magnets were together (my test light turned on), and breaking when separated. The 20-30mm action distance is perfect for my doors and windows.

Installation was straightforward once I understood the sensing distance requirement. They integrated perfectly with my existing security system. While they can't directly power devices (as noted in the description), they provide reliable switch signals to my alarm control panel.

After using these for several weeks through all kinds of weather, they've proven completely reliable with no false alarms. For anyone needing affordable, basic security sensors that just work, these are definitely worth considering.