Amazon.com: Ring Alarm Open Window Magnet (2nd Gen) : Amazon Devices & Accessories
Axial magnetic rings- www.rls.si
Configuration of ring-magnet MFL sensor based on open magnetizing method. | Download Scientific Diagram
Amazon.com: Ring Contact Sensor Riser Spacer - Security Sensor Spacer for Wireless Home Security System, DIY Ring Alarm 2nd Gen Spacer for Door Window Home Security System Accessories, Sensor/Magnet Not Included :