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Some slightly conflicting info on the page for these, so lets clarify that: These are fixed frequency/code and do NOT have a learning function. Your receiver needs to learn the code from these. Not a problem with any of the receivers I used. They work great with both Sonoff RF and some random RF receivers I had lying about. Handy because they use a single 2032 battery rather than the obscure little cylindrical 12V ones that other switches seem to favour. Approx. 5cm across (2 inches). Three smd LEDs inside light up when pressed. They pop apart quite easily to separate the top from the base. They then need to be disassembled to change the battery, but it only needs two small (Phillips/cross head) screws removing to do this. No mounting holes, but easy enough to drill if that is what you want to do. Not particularly robust for outside use, so I wouldn't advise using them for e.g. a doorbell, unless they had significant shelter from rain etc. I didn't do a range check but they worked fine across a 3-4m gap, which is all I needed them to do. Would I buy them again? Yes.
Works verry well and does what is intended to do
good and fast delivery
Very nice buttons. Not big, not small. Installed them on my Home Assistant, using ESP flashed Sonoff Bridge.