Review on Gebildet 10Pcs Plastic Reed Switch Reed Contact Normally Closed Magnetic Induction Switch With 20Pcs Small Multi-Use Round Magnets by Jose Strong

These are very small reed switches - 1/2" x 1/8" x 1/8". These are normally closed (Form B) SPST reed switches that use a bias magnet to hold them in the closed position to hold is indicated by the review written in French.The stronger magnet included in the kit overcomes the biased magnetic field and opens the contact when approached.A small bar in the relay case is a bias magnet and is attached to the side of the Actuator Installed The actuating magnet must be the NS properly aligned for the switch to actuate. You can find this out by connecting an ohmmeter and positioning the components to actuate. Switches will work properly with a variety of magnets including the included in the kit. The problem I have is the actuation range. The magnet should be very close (or touching) to function. The horizontal positioning tolerance over the relay is very tight. The slightest deviation in the horizontal polar positioning will not result in a trip. Using a larger magnet doesn't help. In my application the fit tolerance was too wide to work reliably so I decided to use a normally closed push button switch. If you can control your positional tolerances, this should work.