InterNACHI® LED Microwave Oven Leak Detector

First, remove the indicator from the instruction card, and remove the adhesive from the indicator.
To confirm the appliance’s proper operation, place the indicator inside the microwave oven, off center, next to a glass of water. Operate the microwave according to the manufacturer’s recommendations for no more than 10 seconds. Then, run the indicator around the outside of the closed door to check for leaks. The indicator flashes when microwaves are detected.
InterNACHI® members can order their first device for FREE, at no charge, by requesting it from Chloe at 
Don't forget to give her your shipping address.
Each additional microwave oven leak detector can be ordered from Inspector Outlet:

Purchase as many as you like.
These are a great marketing giveaway that is inspection-related!