Retrofit Ring Contact Sensor First Generation (Use your existing wiring!)

Description

Great way to use existing wiring and not mounting these huge sensors.  Existing wiring will also allow you to use less sensors.  If you have multiple windows/doors in series, you'll only need one retrofit sensor.  Without it, you'll have to mount a sensor per window/door!
This is just like the Ring Retrofit Alarm Kit that monitors 8 zones but you can monitor 1 zone instead.  The first generation contact sensor also comes with a larger battery which is 1550ah whereas generation 2 sensors only come with 235mah batteries.  If you're not mounting these, then the bigger batteries are better!
See video of it in action here:
https://youtu.be/tMvrvyoE1QA