I used this → EDEW 4-Pack Mini Digital Hygrometer
Temperature Humidity Meter for Humidifiers

Amazon Link: https://amzn.to/3Q5rXpW
 

You can buy them at Amazon: https://amzn.to/4aXUVQu
Box: Iris Ohyama, 50L Box B59 x T39 x H29 cm
They are perfect for Fillament. VQu

Also use Silica Gel to dry filament!! 
I used this one from Amazon: https://amzn.to/3Q7iRJv