If you’ve spent thousands of dollars on camera lenses, you might want to protect from extreme conditions or, at least want it to live a long life and serve well.
And there’s a lens cap that can be your ally on this mission. While it functions normally as your good old regular rear cap it also has a built-in hygrometer and thermometer to let you know if the humidity and temperature are too high for your lenses, to help you keep pesky fungus away.

The lens cap first appeared on Japanese blog DC.Watch in November, and the first review was published earlier this month. The lens cap is unimaginatively named UNX-8595, but it’s a pretty unusual product. Basically, it’s a retro-looking thermo-hygrometer attached to the rear lens cap. Since it’s analog, you don’t need any batteries for it.

Fungus is a sneaky and potentially expensive problem for lenses. To prevent this, photographers are advised to invest in a good and reliable dry box for storing photography equipment. The addition of a thermo-hygrometer must have come to makers of this contraption as a cheaper and simpler alternative to a pricey dry box.

The downside is that it’s two times thicker than a regular lens cap, so it takes up a bit more space. And it’s only available for Micro Four Thirds.

As for the price, it costs 1,980 yen ($18 USD) including tax in Japan, and it looks like it can only be bought online from retailers in Japan.

More info on the UN’s website.