The cheapest set of ND filters that you will ever find! 

This 3D printable set of variable ND (neutral density) filters is designed specifically for the CMF Phone 2, allowing you to easily adjust light intake for better photography control. The design uses two polarizing filters stacked together — when rotated relative to each other, they create a variable ND effect by reducing the amount of light passing through. You will have to make 2 circle cutouts from the polarizing sheet.

Here are the 2 sizes of circles that you will need:

21.5mm diameter - for the outer ring

17.5mm diameter - for the inner ring

Here is a link to a cheap sheet of filters that you can use:

🔗 https://www.aliexpress.com/item/1005006916950729.html?spm=a2g0o.order_list.order_list_main.5.17f91802BuALjD

For best results, I would recommend using a 0.2mm nozzle.