This is a small PIR sensor like the ones found on AliExpress. I was using the larger sensors that use the HC-SR501 chip, but these are affected by WiFi interference when used with a board like the ESP-01& ESP-12. These AM312 modules are smaller, run off of 3.3v, and don't have the same false-triggering issue.
This is measured with a caliper for reasonable accuracy, and I created it so I could use it as a placeholder in designs for 3D printed multisensor boxes.
Feel free to use for whatever, and enjoy!